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 A307660 #7 Apr 21 2019 07:50:51
%S A307660 1,-1,-1,-1,-23,139,-929,12011,-54319,664343,7497631,17751799,
%T A307660 -1294263431,13183537379,335384855807,-8293330879261,26192873684641,
%U A307660 -1587651616174289,12035003736999871,-887536237005983377,13114291271436277001,-332542758207041951941,2683832751567973018399
%N A307660 E.g.f. A(x) satisfies: A(x) = exp(-x) * A(x^2)*A(x^3)*A(x^4)* ... *A(x^k)* ...
%F A307660 E.g.f.: exp(-Sum_{n>=1} A074206(k)*x^k).
%F A307660 a(0) = 1; a(n) = -Sum_{k=1..n} A074206(k)*k!*binomial(n-1,k-1)*a(n-k).
%e A307660 E.g.f.: A(x) = 1 - x - x^2/2! - x^3/3! - 23*x^4/4! + 139*x^5/5! - 929*x^6/6! + 12011*x^7/7! - 54319*x^8/! + 664343*x^9/9! + ...
%t A307660 terms = 22; A[_] = 1; Do[A[x_] = Exp[-x] Product[A[x^k], {k, 2, terms}] + O[x]^(terms + 1) // Normal, terms + 1]; CoefficientList[A[x], x] Range[0, terms]!
%Y A307660 Cf. A074206, A129375, A307661.
%K A307660 sign
%O A307660 0,5
%A A307660 _Ilya Gutkovskiy_, Apr 20 2019