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 A381947 #11 Mar 11 2025 08:04:26
%S A381947 1,4,17,111,1001,10507,118986,1411789,17307078,217422098,2784080234,
%T A381947 36201950786,476725871599,6344524132503,85198695369123,
%U A381947 1152990558752089,15708685673520617,215287198676732925,2965962577091646604,41052101428818066604,570583013508324005560
%N A381947 G.f. A(x) satisfies A(x) = B(x*A(x)) / (1 - x)^3, where B(x) is the g.f. of A002293.
%F A381947 a(n) = Sum_{k=0..n} binomial(5*k+1,k) * binomial(n+2*k+2,n-k)/(5*k+1).
%o A381947 (PARI) a(n) = sum(k=0, n, binomial(5*k+1, k)*binomial(n+2*k+2, n-k)/(5*k+1));
%Y A381947 Cf. A162481, A366034, A381944.
%Y A381947 Cf. A002293, A381916.
%K A381947 nonn
%O A381947 0,2
%A A381947 _Seiichi Manyama_, Mar 10 2025