238 (two hundred
ndthirty-eight) is the
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 ...
following
237 and preceding
239
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Year 239 (Roman numerals, CCXXXIX) was a common year starting on Tuesday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Gordianus and Aviola (or, less frequentl ...
.
In mathematics
238 is an
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. ...
.
There are 238
2-vertex-connected graphs on five labeled vertices, and 238 order-5 polydiamonds (
polyiamond
A polyiamond (also polyamond or simply iamond, or sometimes triangular polyomino) is a polyform whose base form is an equilateral triangle. The word ''polyiamond'' is a back-formation from ''diamond'', because this word is often used to describe ...
s that can partitioned into 5 diamonds). Out of the 720 permutations of six elements, exactly 238 of them have a unique
longest increasing subsequence In computer science, the longest increasing subsequence problem is to find a subsequence of a given sequence in which the subsequence's elements are in sorted order, lowest to highest, and in which the subsequence is as long as possible. This subseq ...
.
There are 238
compact and paracompact hyperbolic groups of
ranks 3 through 10.
References
Integers
{{Num-stub