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 A385347 #13 Jun 27 2025 05:50:51
%S A385347 1,3,18,165,2016,30807,564912,12085713,295498368,8128142667,
%T A385347 248419104768,8351633349117,306299582106624,12169801665625887,
%U A385347 520721224401217536,23872081186754865513,1167357853571179216896,60652216264444277244435,3336667444310413833732096
%N A385347 Expansion of e.g.f. 1/(1 - 3 * arcsin(x)).
%F A385347 a(n) = Sum_{k=0..n} 3^k * k! * A385343(n,k).
%F A385347 a(n) ~ sqrt(2*Pi) * cos(1/3) * n^(n + 1/2) / (3 * exp(n) * sin(1/3)^(n+1)). - _Vaclav Kotesovec_, Jun 27 2025
%o A385347 (PARI) my(N=20, x='x+O('x^N)); Vec(serlaplace(1/(1-3*asin(x))))
%Y A385347 Cf. A189780, A385346.
%Y A385347 Cf. A385343.
%K A385347 nonn,easy
%O A385347 0,2
%A A385347 _Seiichi Manyama_, Jun 26 2025