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 A330539 #6 Dec 17 2019 19:14:12
%S A330539 1,1,2,13,48,389,3120,27483,258384,3209481,40895280,532286415,
%T A330539 8095233960,125622532125,2196944928360,40755258858195,773235510112800,
%U A330539 15597078326535825,345588497493916320,7674105262451228055,183908428603335286200
%N A330539 Expansion of e.g.f. Product_{k>=1} (1 + arcsin(x^k)).
%F A330539 E.g.f.: exp(Sum_{k>=1} Sum_{d|k} (-1)^(d + 1) * arcsin(x^(k/d))^d / d).
%t A330539 nmax = 20; CoefficientList[Series[Product[(1 + ArcSin[x^k]), {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]!
%t A330539 nmax = 20; CoefficientList[Series[Exp[Sum[Sum[(-1)^(d + 1) ArcSin[x^(k/d)]^d/d, {d, Divisors[k]}], {k, 1, nmax}]], {x, 0, nmax}], x] Range[0, nmax]!
%Y A330539 Cf. A001818, A270662, A330540.
%K A330539 nonn
%O A330539 0,3
%A A330539 _Ilya Gutkovskiy_, Dec 17 2019