OFFSET
1,3
FORMULA
G.f.: x + x^2 * (1/(1 - x) + Sum_{i>=1} Sum_{j>=1} a(i) * a(j) * x^(i*j)).
MATHEMATICA
a[1] = a[2] = 1; a[n_] := a[n] = 1 + Sum[a[(n - 2)/d] a[d], {d, Divisors[n - 2]}]; Table[a[n], {n, 1, 45}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Jul 05 2021
STATUS
approved