A359004 a(n) = Sum_{d|n} d^(n/d-1) * (n/d)^(d-1).
1, 2, 2, 6, 2, 26, 2, 66, 83, 162, 2, 1250, 2, 898, 4052, 6146, 2, 22106, 2, 74242, 71444, 22530, 2, 771458, 390627, 106498, 1062884, 3039234, 2, 12528122, 2, 17825794, 14289860, 2228226, 75031252, 211754594, 2, 9961474, 179627060, 1185259522, 2, 2237309594, 2
Offset: 1
Keywords
Links
- Seiichi Manyama, Table of n, a(n) for n = 1..5000
Programs
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Mathematica
a[n_] := DivisorSum[n, #^(n/#-1) * (n/#)^(#-1) &]; Array[a, 40] (* Amiram Eldar, Aug 09 2023 *)
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PARI
a(n) = sumdiv(n, d, d^(n/d-1)*(n/d)^(d-1));
Formula
a(n) = [x^n] Sum_{k>0} (n/k)^(k-1) * x^k / (1 - k * x^k).
If p is prime, a(p) = 2.