This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A112680 #20 Jan 21 2020 13:20:20 %S A112680 3,7,8,9,11,16,19,20,23,27,28,31,32,33,36,39,43,44,47,48,49,51,52,57, %T A112680 59,64,67,68,69,71,75,76,79,81,83,87,88,92,93,95,96,100,103,104,107, %U A112680 108,111,115,116,119,121,123,124,127,128,129,131,133,135,136,139,141,147 %N A112680 Numbers which form exclusively the shortest side of primitive Pythagorean triangles. %C A112680 Union of A112398 and A112679. %C A112680 Let S consist of integers x such that x is a term of a primitive Pythagorean triple (ppt). Consider the equivalence classes induced on S by this relation: x and y are equivalent if some ppt includes both x and y. For each class E, let x(E) be the least number in E. Then (a(n)) is the result of arranging the numbers x(E) in increasing order. The terms of S can be represented as nodes of a disconnected graph whose components match the classes C. For example, the component represented by a(1) = 3 starts with %C A112680 . . . . . . . . . 3 %C A112680 . . . . . . . . / ... \ %C A112680 . . . . . . . 4 ------- 5 %C A112680 . . . . . . . . . . . /...\ %C A112680 . . . . . . . . . . 12 -----13 %C A112680 . . . . . . . . . ./...\ .. /..\ %C A112680 . . . . . . . . . 35---37..84--85 %C A112680 - _Clark Kimberling_, Nov 14 2013 %H A112680 Ray Chandler, <a href="/A112680/b112680.txt">Table of n, a(n) for n = 1..10000</a> %H A112680 Ron Knott, <a href="http://www.maths.surrey.ac.uk/hosted-sites/R.Knott/Pythag/pythag.html#moregen">Generator of all Pythagorean triples that include a given number</a> %K A112680 nonn %O A112680 1,1 %A A112680 _Lekraj Beedassy_, Dec 30 2005 %E A112680 Corrected and extended by _Ray Chandler_, Jan 02 2006