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 A030039 #11 Oct 15 2021 21:30:07
%S A030039 1,1,1,2,4,9,21,42,97,233,570,1414,3319,8208,20595,52370,133955,
%T A030039 328261,833652,2136155,5519116,14341917,36069212,93074465,241613666,
%U A030039 630653714,1652472131,4215072482,10985970447,28756470626,75580683613,199201407564,513021407584
%N A030039 a(n+1) = Sum_{k=0..floor(4*n/5)} a(k) * a(n-k).
%H A030039 Seiichi Manyama, <a href="/A030039/b030039.txt">Table of n, a(n) for n = 0..1000</a>
%o A030039 (PARI) lista(nn) = {my(v=vector(nn+2, i, 1)); for(n=1, nn, v[n+2]=sum(k=1, 1+(4*n)\5, v[k]*v[n+2-k])); v; } \\ _Jinyuan Wang_, Mar 18 2020
%Y A030039 Cf. A000992, A030036, A030037, A030038.
%K A030039 nonn
%O A030039 0,4
%A A030039 _N. J. A. Sloane_
%E A030039 More terms from _Jinyuan Wang_, Mar 18 2020