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 A231620 #11 Apr 26 2017 22:58:21
%S A231620 1,1,3,19,277,8641,578949,83316385,25753389181,17098272199297,
%T A231620 24382819596721629,74684329652984094451,491347682599497451569523,
%U A231620 6943240361573523613067995729,210741152533202801182666172606913,13738849457010997118546333815068560833,1923823572225984354415961546862346889944243
%N A231620 a(n) = A000930(n^2), where A000930 is Narayana's cows sequence.
%H A231620 G. C. Greubel, <a href="/A231620/b231620.txt">Table of n, a(n) for n = 0..75</a>
%F A231620 a(n) = [x^(n^2)] 1 / (1 - x - x^3) for n>=0.
%t A231620 Table[SeriesCoefficient[1/(1 - x - x^3), {x, 0, n^2}], {n,0,25}] (* _G. C. Greubel_, Apr 26 2017 *)
%o A231620 (PARI) {a(n) = polcoeff(1/(1-x-x^3 + x*O(x^(n^2))), n^2)}
%o A231620 for(n=0, 20, print1(a(n), ", "))
%Y A231620 Cf. A000930, A231621, A228647, A228648.
%K A231620 nonn
%O A231620 0,3
%A A231620 _Paul D. Hanna_, Nov 13 2013