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 A381879 #10 Mar 09 2025 12:29:03
%S A381879 1,3,16,106,788,6292,52743,457946,4083328,37174786,344142192,
%T A381879 3229827900,30661272627,293907951057,2840826401664,27657352868946,
%U A381879 270968414904700,2669604470832568,26431802684789970,262864480970961882,2624640191306617088,26301183967687772360
%N A381879 Expansion of (1/x) * Series_Reversion( x * (1-x)^2 / C(x) ), where C(x) is the g.f. of A000108.
%F A381879 G.f. A(x) satisfies A(x) = C(x*A(x)) / (1 - x*A(x))^2.
%F A381879 a(n) = Sum_{k=0..n} binomial(n+2*k+1,k) * binomial(3*n-k+1,n-k)/(n+2*k+1).
%o A381879 (PARI) my(N=30, x='x+O('x^N)); Vec(serreverse(x*(1-x)^2*2*x/(1-sqrt(1-4*x)))/x)
%Y A381879 Cf. A381817, A381880.
%Y A381879 Cf. A000108, A381881.
%K A381879 nonn
%O A381879 0,2
%A A381879 _Seiichi Manyama_, Mar 09 2025