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 A371780 #13 Apr 22 2024 13:15:45
%S A371780 1,7,66,681,7337,81081,911153,10361554,118881714,1373402934,
%T A371780 15954079557,186165866937,2180501226751,25620628577083,
%U A371780 301858589475117,3564841627421691,42186363329210473,500142626996777355,5939062937833796486,70626949319708756435
%N A371780 a(n) = Sum_{k=0..floor(n/3)} binomial(5*n+2,n-3*k).
%H A371780 Robert Israel, <a href="/A371780/b371780.txt">Table of n, a(n) for n = 0..918</a>
%F A371780 a(n) = [x^n] 1/(((1-x)^3-x^3) * (1-x)^(4*n)).
%p A371780 f:= proc(n) local k; add(binomial(5*n+2,n-3*k),k=0..n/3); end proc:
%p A371780 map(f, [$0..100]); # _Robert Israel_, Apr 22 2024
%o A371780 (PARI) a(n) = sum(k=0, n\3, binomial(5*n+2, n-3*k));
%Y A371780 Cf. A371777, A371778, A371779.
%Y A371780 Cf. A371739.
%K A371780 nonn
%O A371780 0,2
%A A371780 _Seiichi Manyama_, Apr 05 2024