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 A371786 #8 Apr 06 2024 10:03:56
%S A371786 1,4,27,209,1716,14553,125971,1105885,9809019,87691592,788832045,
%T A371786 7131655908,64743390321,589808771881,5389066722654,49365637128655,
%U A371786 453212161425716,4168951499299185,38415242186255419,354527945536409116,3276414018301664025
%N A371786 a(n) = Sum_{k=0..floor(n/2)} (-1)^k * binomial(4*n-k,n-2*k).
%F A371786 a(n) = [x^n] 1/((1-x+x^2) * (1-x)^(3*n)).
%o A371786 (PARI) a(n) = sum(k=0, n\2, (-1)^k*binomial(4*n-k, n-2*k));
%Y A371786 Cf. A024718, A371785, A371787.
%Y A371786 Cf. A371743.
%K A371786 nonn
%O A371786 0,2
%A A371786 _Seiichi Manyama_, Apr 06 2024