OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..387
FORMULA
For prime p, a(p) = p^p + 1; A125137 is a subsequence. - Michel Marcus, Nov 20 2015
a(n) = Sum_{d|n, gcd(d,n/d)=1} d^n. - Wesley Ivan Hurt, Apr 28 2023
MATHEMATICA
a[n_, k_] := Sum[If[GCD[i, n] == i && GCD[i, n/i] == 1, i^k, 0], {i, n}]; Table[a[n, n], {n, 1, 24}]
a[1] = 1; a[n_] := Times @@ (1 + First[#]^(n * Last[#]) &/@ FactorInteger[n]); Array[a, 19] (* Amiram Eldar, Aug 10 2019 *)
PROG
(PARI) a(n) = sumdiv(n, d, d^n*(gcd(d, n/d) == 1)); \\ Michel Marcus, Mar 19 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
José María Grau Ribas, Mar 07 2014
STATUS
approved