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 A088558 #10 Mar 05 2020 08:21:55
%S A088558 3,15,5,63,21,7,45,255,77,9,117,55,165,33,11,1023,285,65,357,39,13,
%T A088558 105,525,247,621,153,725,15,837,119,957,4095,85,273,51,17,1365,345,
%U A088558 133,231,1677,95,1845,57,19,513,2205,1015,2397,609,253,105,2805,713,21,207,325
%N A088558 Least odd leg of primitive Pythagorean triangles with even leg 4n.
%H A088558 Jean-François Alcover, <a href="/A088558/b088558.txt">Table of n, a(n) for n = 1..1000</a>
%t A088558 a[n_] := 2k + 1 /. Solve[k > 0 && 1 < h < 2k + 1 + 4n && (2k + 1)^2 + (4n)^2 == h^2 && GCD[2k + 1, 4n, h] == 1, {k, h}, Integers][[1]];
%t A088558 a /@ Range[57] (* _Jean-François Alcover_, Mar 05 2020 *)
%Y A088558 Cf. A088557, A096891-A096900.
%K A088558 nonn
%O A088558 1,1
%A A088558 _Lekraj Beedassy_, Nov 17 2003
%E A088558 Extended by _Ray Chandler_, Jul 14 2004