A337186 a(n) = 1 + Sum_{k=0..n-2} binomial(n-2,k) * a(k).
1, 1, 2, 3, 6, 14, 36, 101, 308, 1013, 3562, 13300, 52482, 218045, 950614, 4335563, 20628882, 102153978, 525383324, 2801105889, 15455435864, 88117352141, 518391612686, 3142762585120, 19611454375090, 125829007917417, 829254498014570, 5608225148263459
Offset: 0
Keywords
Programs
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Mathematica
a[n_] := a[n] = 1 + Sum[Binomial[n - 2, k] a[k], {k, 0, n - 2}]; Table[a[n], {n, 0, 27}]
Formula
G.f. A(x) satisfies: A(x) = (1/(1 - x)) * (1 + x^2 * A(x/(1 - x))).