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A346116
a(1) = a(2) = 1; a(n+2) = 1 + Sum_{d|n} a(n/d) * a(d).
0
1, 1, 2, 3, 5, 8, 11, 21, 23, 49, 51, 109, 103, 247, 207, 517, 435, 1086, 871, 2251, 1743, 4631, 3531, 9365, 7063, 19081, 14152, 38369, 28397, 77299, 56795, 155289, 113591, 311739, 227387, 624349, 454885, 1251509, 909771, 2504761, 1819955, 5014529, 3639911, 10033709, 7279823
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