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 A076601 #10 May 11 2018 01:42:03
%S A076601 3,4,5,12,13,84,85,3612,3613,6526884,6526885,21300113901612,
%T A076601 21300113901613,226847426110843688722000884,
%U A076601 226847426110843688722000885,25729877366557343481074291996721923093306518970391612,25729877366557343481074291996721923093306518970391613
%N A076601 a(1)=3, a(n_even)=(a(n-1)^2-1)/2; a(n_odd)=a(n-1)+1.
%C A076601 {3, 4, 5}, {5, 12, 13}, {13, 84, 85}... are sides {a<b<c} of the right triangles, with hypotenuse c=b+1.
%t A076601 Transpose[NestList[{#[[1]]+1,If[EvenQ[#[[1]]+1],(#[[2]]^2-1)/2,#[[2]]+1]}&,{1,3},20]][[2]] (* _Harvey P. Dale_, May 02 2012 *)
%K A076601 easy,nonn
%O A076601 1,1
%A A076601 _Zak Seidov_, Oct 21 2002
%E A076601 More terms from _Harvey P. Dale_, May 02 2012