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 A383537 #8 Apr 29 2025 08:54:45
%S A383537 1,1,1,17,51,109,981,4209,12637,79351,393493,1454021,7686459,39697057,
%T A383537 166999101,823144689,4241896917,19293138685,93151760599,473739765167,
%U A383537 2252548154403,10877558634801,54682637188009,266304982300197,1295171619802551,6466091747859771
%N A383537 a(n) = Sum_{k=0..floor(n/3)} binomial(n+k,k)^2 * binomial(n-2*k,k).
%C A383537 Diagonal of the rational function 1 / ((1-x)*(1-y)*(1-z) - z^3).
%o A383537 (PARI) a(n) = sum(k=0, n\3, binomial(n+k, k)^2*binomial(n-2*k, k));
%Y A383537 Cf. A383538.
%K A383537 nonn
%O A383537 0,4
%A A383537 _Seiichi Manyama_, Apr 29 2025