A317853 a(1) = 1; a(n > 1) = Sum_{0 < k < n} (-1)^(n - k - 1) a(n - k) Sum_{d|k} a(d).

1, 1, 1, 1, 2, 2, 5, 6, 11, 14, 23, 26, 51, 70, 114, 147, 237, 314, 516, 715, 1118, 1549, 2353, 3252, 5011, 7235, 10724, 15142, 22504, 32506, 47770, 69173, 100980, 146657, 212504, 308563, 448256, 658037, 946166, 1373739, 1988283, 2919185, 4197886, 6118850

Offset

1,5

Links

Table of n, a(n) for n=1..44.

Mathematica

a[n_]:=a[n]=If[n==1, 1, Sum[(-1)^(n-k-1)*a[n-k]*Sum[a[d], {d, Divisors[k]}], {k, n-1}]];
Array[a, 50]

Crossrefs

Cf. A001003, A001678, A002033, A003238, A052893, A053492, A067824, A167865, A214577, A277996, A280000, A317875.

Cf. A317876, A317877, A317878, A317879, A317880, A317881.

Cf. A317882, A317883, A317884, A317885.

Sequence in context: A007988 A241449 A240184 * A238517 A335240 A356367

Adjacent sequences: A317850 A317851 A317852 * A317854 A317855 A317856

Keyword

nonn

Author

Gus Wiseman, Aug 09 2018

Status

approved