OFFSET
1,2
FORMULA
If p is prime, a(p) = p^p + 1. See A125137. - Bernard Schott, Oct 18 2021
EXAMPLE
a(4) = 1060; a(4) = (4^1)' + (4^2)' + (4^4)' = 4' + 16' + 256' = 4 + 32 + 1024 = 1060.
MATHEMATICA
d[0] = d[1] = 0; d[n_] := n * Plus @@ ((Last[#]/First[#]) & /@ FactorInteger[n]); a[n_] := DivisorSum[n, d[n^#] &]; Array[a, 20] (* Amiram Eldar, Oct 16 2021 *)
PROG
(PARI) ad(n) = vecsum([n/f[1]*f[2]|f<-factor(n+!n)~]); \\ A003415
a(n) = sumdiv(n, d, ad(n^d)); \\ Michel Marcus, Oct 18 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Oct 16 2021
STATUS
approved