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 A078927 #26 Jun 14 2018 02:23:22 %S A078927 6,858,7140,158730,771342,3120180,9699690,31651620,119584290, %T A078927 198843645,229474245,406816410,281291010,1412220810,1673196525, %U A078927 3457939485,3234846615,4360010655,4573403835,4127218095,11532931410,12929686770,101268227775 %N A078927 Smallest s for which there are exactly n primitive Pythagorean triangles with perimeter 2s; i.e., smallest s such that A078926(s) = n. %C A078927 A Pythagorean triangle is a right triangle whose edge lengths are all integers; such a triangle is 'primitive' if the lengths are relatively prime. %H A078927 Derek J. C. Radden and Peter T. C. Radden, <a href="/A078927/b078927.txt">Table of n, a(n) for n=1..39</a> (terms 1 through 15 were computed by Derek J. C. Radden) %e A078927 a(2)=858; the primitive Pythagorean triangles with edge lengths (364, 627, 725) and (195, 748, 773) both have perimeter 2*858 = 1716. %t A078927 oddpart[n_] := If[OddQ[n], n, oddpart[n/2]]; ct[p_] := Length[Select[Divisors[oddpart[p/2]], p/2<#^2<p&&GCD[ #, p/2/# ]==1&]]; a[n_] := For[s=1, True, s++, If[ct[2s]==n, Return[s]]] %Y A078927 a(n) = A078928(n)/2. Cf. A078926. %K A078927 nonn %O A078927 1,1 %A A078927 _Dean Hickerson_, Dec 15 2002 %E A078927 a(8) from _Robert G. Wilson v_, Dec 19 2002 %E A078927 a(9)-a(15) from _Derek J C Radden_, Dec 22 2012 %E A078927 a(16)-a(23) from _Peter T. C. Radden_, Dec 29 2012