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 A088557 #10 Mar 05 2020 08:21:38
%S A088557 4,12,24,40,60,84,8,144,180,20,264,312,364,420,480,56,12,684,80,840,
%T A088557 924,28,1104,1200,140,1404,48,176,1740,1860,16,72,2244,260,2520,2664,
%U A088557 308,36,3120,3280,3444,132,416,3960,60,476,168,4704,20,5100,5304,88,5724,5940
%N A088557 Least even leg of primitive Pythagorean triangles with odd leg 2n+1.
%C A088557 a(n) shares identical entries with A046092(n) except for n=(A081934 - 1)/2.
%H A088557 Jean-François Alcover, <a href="/A088557/b088557.txt">Table of n, a(n) for n = 1..1000</a>
%t A088557 a[n_] := 2k /. Solve[k > 0 && 1 < h < 2k + 2n + 1 && (2k)^2 + (2n + 1)^2 == h^2 && GCD[2k, 2n + 1, h] == 1, {k, h}, Integers][[1]];
%t A088557 a /@ Range[54] (* _Jean-François Alcover_, Mar 05 2020 *)
%Y A088557 Cf. A088558, A096891-A096900.
%K A088557 nonn
%O A088557 1,1
%A A088557 _Lekraj Beedassy_, Nov 17 2003
%E A088557 Corrected and extended by _Ray Chandler_, Jul 14 2004