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 A381882 #10 Mar 09 2025 12:26:24
%S A381882 1,4,24,175,1428,12525,115468,1103777,10844715,108860766,1111722956,
%T A381882 11514401451,120666441067,1277161022725,13633269293868,
%U A381882 146606818816257,1586739194404521,17271207134469417,188942438655850740,2076317084779878706,22909617070555385010
%N A381882 Expansion of (1/x) * Series_Reversion( x / ((1+x)^3 * C(x)) ), where C(x) is the g.f. of A000108.
%F A381882 G.f. A(x) satisfies A(x) = (1 + x*A(x))^3 * C(x*A(x)).
%F A381882 a(n) = Sum_{k=0..n} binomial(n+2*k+1,k) * binomial(3*n+3,n-k)/(n+2*k+1).
%F A381882 a(n) = binomial(3*(1 + n), n)*hypergeom([(1+n)/2, 1+n/2, -n], [2 + n, 4 + 2*n], -4)/(1 + n). - _Stefano Spezia_, Mar 09 2025
%o A381882 (PARI) my(N=30, x='x+O('x^N)); Vec(serreverse(x/((1+x)^3*(1-sqrt(1-4*x))/(2*x)))/x)
%Y A381882 Cf. A054727, A381881.
%Y A381882 Cf. A000108, A381880.
%K A381882 nonn
%O A381882 0,2
%A A381882 _Seiichi Manyama_, Mar 09 2025