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 A277469 #11 Nov 08 2017 02:31:49
%S A277469 0,1,2,13,112,1329,19344,336533,6778752,155247777,3980956800,
%T A277469 112984562813,3515475849216,118984054897681,4351800687259648,
%U A277469 171034439586509445,7188243684485414912,321696219477456836929,15273278824827215388672,766732102664665113137517
%N A277469 E.g.f.: arcsin(x)/(1 + LambertW(-x)).
%H A277469 G. C. Greubel, <a href="/A277469/b277469.txt">Table of n, a(n) for n = 0..385</a>
%F A277469 a(n) ~ arcsin(exp(-1)) * n^n.
%t A277469 CoefficientList[Series[ArcSin[x]/(1+LambertW[-x]), {x, 0, 25}], x] * Range[0, 25]!
%t A277469 Flatten[{0, Table[(1-(-1)^n)/2 * (n-2)!!^2 + Sum[Binomial[n, k] * (1-(-1)^k)/2 * (k-2)!!^2 * (n-k)^(n-k), {k, 1, n-1}], {n, 1, 25}]}] (* _Vaclav Kotesovec_, Oct 28 2016 *)
%o A277469 (PARI) x='x+O('x^50); concat([0], Vec(serlaplace(asin(x)/(1 + lambertw(-x))))) \\ _G. C. Greubel_, Nov 07 2017
%Y A277469 Cf. A000312, A086331, A277470.
%K A277469 nonn
%O A277469 0,3
%A A277469 _Vaclav Kotesovec_, Oct 16 2016