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 A076604 #8 Apr 17 2022 20:12:59
%S A076604 11,60,61,1860,1861,1731660,1731661,1499324909460,1499324909461,
%T A076604 1123987592065117923655260,1123987592065117923655261,
%U A076604 631674053558170970207436821512098200057586489060
%N A076604 a(1) = 11, a(n_even) = (a(n-1)^2-1)/2; a(n_odd) = a(n-1)+1.
%C A076604 {11, 60, 61}, {61, 1860, 1861}, {1861, 1731660, 1731661}... are sides {a<b<c} of the right triangles, with hypotenuse c = b+1.
%K A076604 easy,nonn
%O A076604 1,1
%A A076604 _Zak Seidov_, Oct 21 2002
%E A076604 a(12) from _Lars Blomberg_, Oct 08 2008