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A351707
G.f. A(x) satisfies: A(x) = 1 + x + x^2 + x^3 + x^4 * A(x/(1 - x)) / (1 - x)^2.
3
1, 1, 1, 1, 1, 3, 7, 15, 31, 65, 147, 373, 1051, 3157, 9761, 30573, 96965, 313999, 1049719, 3654303, 13284783, 50268837, 196638987, 789611161, 3238765671, 13540348965, 57710600953, 251163156089, 1118308871001, 5100825621147, 23838465463447, 114044805729151
OFFSET
0,6
FORMULA
a(0) = ... = a(3) = 1; a(n) = Sum_{k=0..n-4} binomial(n-3,k+1) * a(k).
MATHEMATICA
nmax = 31; A[_] = 0; Do[A[x_] = 1 + x + x^2 + x^3 + x^4 A[x/(1 - x)]/(1 - x)^2 + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
a[n_] := a[n] = If[n < 4, 1, Sum[Binomial[n - 3, k + 1] a[k], {k, 0, n - 4}]]; Table[a[n], {n, 0, 31}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Feb 16 2022
STATUS
approved