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%I #8 Jan 29 2021 10:29:33
%S 1,1,2,3,6,14,36,101,308,1013,3562,13300,52482,218045,950614,4335563,
%T 20628882,102153978,525383324,2801105889,15455435864,88117352141,
%U 518391612686,3142762585120,19611454375090,125829007917417,829254498014570,5608225148263459
%N a(n) = 1 + Sum_{k=0..n-2} binomial(n-2,k) * a(k).
%F G.f. A(x) satisfies: A(x) = (1/(1 - x)) * (1 + x^2 * A(x/(1 - x))).
%t a[n_] := a[n] = 1 + Sum[Binomial[n - 2, k] a[k], {k, 0, n - 2}]; Table[a[n], {n, 0, 27}]
%Y Cf. A000994, A007476, A186021.
%K nonn
%O 0,3
%A _Ilya Gutkovskiy_, Jan 29 2021
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