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206 (number)
206 (two hundred ndsix) is the natural number following 205 and preceding 207. In mathematics 206 is both a nontotient and a noncototient. 206 is an untouchable number. It is the lowest positive integer (when written in English as "two hundred and six") to employ all of the vowels once only, not including Y. The other numbers sharing this property are 230, 250, 260, 602, 640, 5000, 8000, 9000, 80,000 and 90,000. 206 and 207 form the second pair of consecutive numbers (after 14 and 15) whose sums of divisors are equal. There are exactly 206 different linear forests on five labeled nodes, and exactly 206 regular semigroups of order four up to isomorphism and anti-isomorphism. In science There are 206 bones in the typical adult human body.. See also * The Year 206 AD * Cessna 206, a single engine light aircraft * Bell 206, a light helicopter * The Peugeot 206, a French supermini automobile * US Area code 206, and The 206 slang terminology for the urban part of the greater ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Natural Number
In mathematics, the natural numbers are those numbers used for counting (as in "there are ''six'' coins on the table") and ordering (as in "this is the ''third'' largest city in the country"). Numbers used for counting are called ''Cardinal number, cardinal numbers'', and numbers used for ordering are called ''Ordinal number, ordinal numbers''. Natural numbers are sometimes used as labels, known as ''nominal numbers'', having none of the properties of numbers in a mathematical sense (e.g. sports Number (sports), jersey numbers). Some definitions, including the standard ISO/IEC 80000, ISO 80000-2, begin the natural numbers with , corresponding to the non-negative integers , whereas others start with , corresponding to the positive integers Texts that exclude zero from the natural numbers sometimes refer to the natural numbers together with zero as the whole numbers, while in other writings, that term is used instead for the integers (including negative integers). The natural ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
205 (number)
205 (two hundred ndfive) is the natural number following 204 and preceding 206. In mathematics 205 is a lucky number, and a Wolstenholme number. On an infinite chessboard, a knight can reach exactly 205 squares within four moves. There are 205 different ways of forming a connected graph by adding six edges to a set of five labeled vertices. In other fields * The atomic number of an element temporarily calleBinilpentium See also * List of highways numbered 205 * 205 Martha, a large Main belt asteroid * 205 Yonge Street, a building in Toronto * 205 series, a commuter train type in Japan * Peugeot 205, a French car * WWE 205 Live ''WWE 205 Live'' is an American professional wrestling streaming television program that was produced by WWE. It premiered on November 29, 2016, and ended on February 11, 2022. The show originally aired exclusively on the WWE Network until March ..., an American professional wrestling program References {{DEFAULTSORT:205 (Number) Integers< ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
207 (number)
207 (two hundred ndseven) is the natural number following 206 and preceding 208. It is an odd composite number with a prime factorization of 3^2\cdot 23. In Mathematics 207 is a Wedderburn-Etherington number. There are exactly 207 different matchstick graphs with eight edges. 207 is also a deficient number, as 207's proper divisors (divisors not including the number itself) only add up to 105: 1+3+9+23+69=105<207. See also *Peugeot 207
The Peugeot 207 is a supermini car ( B) that was designed and produced by the French automaker Peugeot from 2006 to 2014. It was presented at the Geneva Motor Show in 2006, and entered production in April 2006, as the successor to the Peugeo ...
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Nontotient
In number theory, a nontotient is a positive integer ''n'' which is not a totient number: it is not in the range of Euler's totient function φ, that is, the equation φ(''x'') = ''n'' has no solution ''x''. In other words, ''n'' is a nontotient if there is no integer ''x'' that has exactly ''n'' coprimes below it. All odd numbers are nontotients, except 1, since it has the solutions ''x'' = 1 and ''x'' = 2. The first few even nontotients are : 14, 26, 34, 38, 50, 62, 68, 74, 76, 86, 90, 94, 98, 114, 118, 122, 124, 134, 142, 146, 152, 154, 158, 170, 174, 182, 186, 188, 194, 202, 206, 214, 218, 230, 234, 236, 242, 244, 246, 248, 254, 258, 266, 274, 278, 284, 286, 290, 298, ... Least ''k'' such that the totient of ''k'' is ''n'' are (0 if no such ''k'' exists) :1, 3, 0, 5, 0, 7, 0, 15, 0, 11, 0, 13, 0, 0, 0, 17, 0, 19, 0, 25, 0, 23, 0, 35, 0, 0, 0, 29, 0, 31, 0, 51, 0, 0, 0, 37, 0, 0, 0, 41, 0, 43, 0, 69, 0, 47, 0, 65, 0, 0, 0, 53, 0, 81, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Noncototient
In mathematics, a noncototient is a positive integer ''n'' that cannot be expressed as the difference between a positive integer ''m'' and the number of coprime integers below it. That is, ''m'' − φ(''m'') = ''n'', where φ stands for Euler's totient function, has no solution for ''m''. The ''cototient'' of ''n'' is defined as ''n'' − φ(''n''), so a noncototient is a number that is never a cototient. It is conjectured that all noncototients are even. This follows from a modified form of the slightly stronger version of the Goldbach conjecture: if the even number ''n'' can be represented as a sum of two distinct primes ''p'' and ''q,'' then :pq - \varphi(pq) = pq - (p-1)(q-1) = p+q-1 = n-1. \, It is expected that every even number larger than 6 is a sum of two distinct primes, so probably no odd number larger than 5 is a noncototient. The remaining odd numbers are covered by the observations 1=2-\phi(2), 3 = 9 - \phi(9) and 5 = 25 - ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Untouchable Number
An untouchable number is a positive integer that cannot be expressed as the sum of all the proper divisors of any positive integer (including the untouchable number itself). That is, these numbers are not in the image of the aliquot sum function. Their study goes back at least to Abu Mansur al-Baghdadi (circa 1000 AD), who observed that both 2 and 5 are untouchable. Examples For example, the number 4 is not untouchable as it is equal to the sum of the proper divisors of 9: 1 + 3 = 4. The number 5 is untouchable as it is not the sum of the proper divisors of any positive integer: 5 = 1 + 4 is the only way to write 5 as the sum of distinct positive integers including 1, but if 4 divides a number, 2 does also, so 1 + 4 cannot be the sum of all of any number's proper divisors (since the list of factors would have to contain both 4 and 2). The first few untouchable numbers are: : 2, 5, 52, 88, 96, 120, 124, 146, 162, 188, 2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Divisor Function
In mathematics, and specifically in number theory, a divisor function is an arithmetic function related to the divisors of an integer. When referred to as ''the'' divisor function, it counts the ''number of divisors of an integer'' (including 1 and the number itself). It appears in a number of remarkable identities, including relationships on the Riemann zeta function and the Eisenstein series of modular forms. Divisor functions were studied by Ramanujan, who gave a number of important Modular arithmetic, congruences and identity (mathematics), identities; these are treated separately in the article Ramanujan's sum. A related function is the divisor summatory function, which, as the name implies, is a sum over the divisor function. Definition The sum of positive divisors function σ''z''(''n''), for a real or complex number ''z'', is defined as the summation, sum of the ''z''th Exponentiation, powers of the positive divisors of ''n''. It can be expressed in Summation#Capital ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tree (graph Theory)
In graph theory In mathematics, graph theory is the study of ''graphs'', which are mathematical structures used to model pairwise relations between objects. A graph in this context is made up of '' vertices'' (also called ''nodes'' or ''points'') which are conne ..., a tree is an undirected graph in which any two Vertex (graph theory), vertices are connected by ''exactly one'' Path (graph theory), path, or equivalently a Connected graph, connected Cycle (graph theory), acyclic undirected graph. A forest is an undirected graph in which any two vertices are connected by ''at most one'' path, or equivalently an acyclic undirected graph, or equivalently a Disjoint union of graphs, disjoint union of trees. A polytreeSee . (or directed tree or oriented treeSee .See . or singly connected networkSee .) is a directed acyclic graph (DAG) whose underlying undirected graph is a tree. A polyforest (or directed forest or oriented forest) is a directed acyclic graph whose underlying undirecte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Regular Semigroup
In mathematics, a regular semigroup is a semigroup ''S'' in which every element is regular, i.e., for each element ''a'' in ''S'' there exists an element ''x'' in ''S'' such that . Regular semigroups are one of the most-studied classes of semigroups, and their structure is particularly amenable to study via Green's relations. History Regular semigroups were introduced by J. A. Green in his influential 1951 paper "On the structure of semigroups"; this was also the paper in which Green's relations were introduced. The concept of ''regularity'' in a semigroup was adapted from an analogous condition for rings, already considered by John von Neumann. It was Green's study of regular semigroups which led him to define his celebrated relations. According to a footnote in Green 1951, the suggestion that the notion of regularity be applied to semigroups was first made by David Rees. The term inversive semigroup (French: demi-groupe inversif) was historically used as synonym in the pap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cessna 206
The Cessna 205, 206, and 207, known primarily as the Stationair (and marketed variously as the Super Skywagon, Skywagon and Super Skylane) are a family of single-engined, general aviation aircraft with fixed landing gear, used in commercial air service as well as for personal use. The family was originally developed from the popular retractable-gear Cessna 210 and produced by the Cessna, Cessna Aircraft Company. The line's combination of a powerful engine, rugged construction and a large cabin has made these aircraft popular bush planes. Cessna describes the 206 as "the sport-utility vehicle of the air." These airplanes are also used for aerial photography, skydiving and other utility purposes. They can also be equipped with floats, amphibious floats and skis. Alternatively, they can be fitted with luxury appointments for use as a personal air transport. From 1962 to 2006 Cessna produced 8,509 aircraft in the 205, 206 and 207 variants. The aircraft remains in production. D ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bell 206
The Bell 206 is a family of two-bladed, single- and twin-engined helicopters, manufactured by Bell Helicopter at its Mirabel, Quebec, plant. Originally developed as the Bell YOH-4 for the United States Army's Light Observation Helicopter program, it was not selected by the Army. Bell redesigned the airframe and successfully marketed the aircraft commercially as the five-place Bell 206A JetRanger. The new design was eventually selected by the Army as the OH-58 Kiowa. Bell also developed a seven-place LongRanger, which was later offered with a twin-engined option as the TwinRanger, while Tridair Helicopters offers a similar conversion of the LongRanger called the Gemini ST. The ICAO-assigned model designation "B06" is used on flight plans for the JetRanger and LongRanger, and the designation "B06T" is used for the twin-engined TwinRangers. Development Origins and JetRanger On October 14, 1960, the United States Navy solicited responses from 25 aircraft manufacturers to a req ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peugeot 206
The Peugeot 206 is a supermini car (B-segment) designed and produced by the French car manufacturer Peugeot since May 1998 as a replacement to the Peugeot 205. Developed under the codename ''T1'', it was released in September 1998 in hatchback form, which was followed by coupé cabriolet (206 CC) in September 2000, station wagon (206 SW) in September 2001, and a sedan version (206 SD) in September 2005, before being replaced by the 207 in April 2006. Its facelifted version was initially launched in South America in September 2008, and in China in November 2008, in hatchback, sedan and station wagon body styles, and marketed as the 207 Compact, and as the 207 respectively. This version was subsequently launched in Europe in February 2009, only in hatchback form and marketed as the 206+. In South America it continued to be offered as the 207 Compact nameplate until January 2017, and furthermore in China, both under the 207 nameplate and as the Citroën C2. The 206 is the best- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
