A348146 a(n) = Sum_{d|n} (d!)^(n-d).
1, 2, 2, 6, 2, 234, 2, 331842, 46658, 24883200258, 2, 139314179589392898, 2, 82606411253903523840004098, 619173642242176782338, 6984964247141514123665660725036072962, 2, 109110688415571335888754861121236891599318185050114, 2
Offset: 1
Keywords
Links
- Seiichi Manyama, Table of n, a(n) for n = 1..61
Programs
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Mathematica
Table[Sum[(i!)^(n - i) (1 - Ceiling[n/i] + Floor[n/i]), {i, n}], {n, 20}] -
PARI
a(n) = sumdiv(n, d, d!^(n-d)); \\ Seiichi Manyama, Oct 03 2021
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PARI
my(N=20, x='x+O('x^N)); Vec(sum(k=1, N, x^k/(1-(k!*x)^k))) \\ Seiichi Manyama, Oct 03 2021
Formula
a(p) = 2 for primes p.
G.f.: Sum_{k>=1} x^k/(1 - (k! * x)^k). - Seiichi Manyama, Oct 03 2021