A369912 a(n) = Sum_{p|n, p prime} p^sopf(n/p).
0, 1, 1, 4, 1, 17, 1, 4, 27, 57, 1, 41, 1, 177, 368, 4, 1, 251, 1, 153, 2530, 2169, 1, 41, 3125, 8361, 27, 561, 1, 5568, 1, 4, 178478, 131361, 94932, 275, 1, 524649, 1596520, 153, 1, 37514, 1, 8313, 6686, 8389137, 1, 41, 823543, 78157, 129145076, 32937, 1, 251
Offset: 1
Programs
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Mathematica
a[n_] := Sum[p, {p, Select[Divisors[n], PrimeQ]}]; Table[DivisorSum[n, #^a[n/#] &, PrimeQ[#] &], {n, 80}]
Formula
a(p^k) = p^(p-p*floor(1/k)) for p prime and k>=1. - Wesley Ivan Hurt, Jul 09 2025
Comments