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A328424
a(1) = 1; a(n) = Sum_{d|n, d < n} p(n/d) * a(d), where p = A000041 (partition numbers).
2
1, 2, 3, 9, 7, 23, 15, 50, 39, 70, 56, 187, 101, 195, 218, 420, 297, 625, 490, 949, 882, 1226, 1255, 2533, 2007, 2840, 3217, 4588, 4565, 6966, 6842, 10099, 10479, 13498, 15093, 21507, 21637, 27975, 31791, 41722, 44583, 58022, 63261, 80415, 90799, 110578, 124754
OFFSET
1,2
LINKS
FORMULA
G.f. A(x) satisfies: A(x) = x + Sum_{k>=2} p(k) * A(x^k).
a(n) ~ exp(Pi*sqrt(2*n/3)) / (4*sqrt(3)*n). - Vaclav Kotesovec, Oct 16 2019
MATHEMATICA
a[n_] := If[n == 1, n, Sum[If[d < n, PartitionsP[n/d] a[d], 0], {d, Divisors[n]}]]; Table[a[n], {n, 1, 47}]
terms = 47; A[_] = 0; Do[A[x_] = x + Sum[PartitionsP[k] A[x^k], {k, 2, terms}] + O[x]^(terms + 1) // Normal, terms + 1]; CoefficientList[A[x], x] // Rest
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Oct 15 2019
STATUS
approved