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 A372104 #6 Apr 19 2024 10:30:53
%S A372104 1,2,12,86,686,5858,52404,484814,4600652,44534386,438034928,
%T A372104 4365350062,43983695242,447305878226,4585518132768,47335424695142,
%U A372104 491615988964766,5133343692822146,53858312462193328,567501135052136702,6002857276349252630
%N A372104 G.f. A(x) satisfies A(x) = 1/( 1 - 4*x*A(x)/(1-x) )^(1/2).
%F A372104 a(n) = Sum_{k=0..n} 4^k * binomial(3*k/2-1/2,k) * binomial(n-1,n-k)/(k+1).
%o A372104 (PARI) a(n) = sum(k=0, n, 4^k*binomial(3*k/2-1/2, k)*binomial(n-1, n-k)/(k+1));
%Y A372104 Cf. A085362, A372086.
%K A372104 nonn
%O A372104 0,2
%A A372104 _Seiichi Manyama_, Apr 18 2024