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 A378461 #7 Nov 27 2024 08:06:06
%S A378461 1,2,16,137,1216,11057,102229,956601,9032680,85893860,821402341,
%T A378461 7891371303,76105710253,736364519399,7144586617597,69487754788517,
%U A378461 677259385478616,6613163312601491,64681617534027028,633569272646345064,6214190349161222941,61023489213944162889
%N A378461 a(n) = Sum_{k=0..n} binomial(n+k-1,k) * binomial(2*n+2*k-1,n-k).
%F A378461 a(n) = [x^n] 1/(1 - x - x/(1 - x)^2)^n.
%o A378461 (PARI) a(n) = sum(k=0, n, binomial(n+k-1, k)*binomial(2*n+2*k-1, n-k));
%Y A378461 Cf. A009723, A378460.
%Y A378461 Cf. A378466.
%K A378461 nonn
%O A378461 0,2
%A A378461 _Seiichi Manyama_, Nov 27 2024