A341697 a(1) = a(2) = 1; a(n+1) = Sum_{d|n, d < n} a(n/d) * a(d).

1, 1, 1, 1, 2, 2, 4, 4, 6, 7, 11, 11, 17, 17, 25, 29, 38, 38, 54, 54, 72, 80, 102, 102, 136, 140, 174, 186, 228, 228, 300, 300, 366, 388, 464, 480, 594, 594, 702, 736, 874, 874, 1068, 1068, 1250, 1324, 1528, 1528, 1828, 1844, 2144, 2220, 2534, 2534, 2982, 3026, 3464, 3572, 4028, 4028

Offset

1,5

Links

Table of n, a(n) for n=1..60.

Mathematica

a[1] = a[2] = 1; a[n_] := a[n] = Sum[If[d < (n - 1), a[(n - 1)/d] a[d], 0], {d, Divisors[n - 1]}]; Table[a[n], {n, 60}]

Prog

(PARI) A341697(n) = if(n<3, 1, sumdiv(n-1, d, if(d<(n-1), A341697((n-1)/d)*A341697(d), 0))); \\ Antti Karttunen, Feb 17 2021

Crossrefs

Cf. A038044, A122698, A333051, A341698.

Sequence in context: A067772 A078374 A366129 * A242984 A027590 A007212

Adjacent sequences: A341694 A341695 A341696 * A341698 A341699 A341700

Keyword

nonn

Author

Ilya Gutkovskiy, Feb 17 2021

Status

approved