OFFSET
1,1
FORMULA
a(n) = Sum_{d|n} (n/d)^n * binomial(d+2,2).
MATHEMATICA
a[n_] := DivisorSum[n, (n/#)^n * Binomial[# + 2, 2] &]; Array[a, 20] (* Amiram Eldar, Jul 17 2023 *)
PROG
(PARI) a(n) = sumdiv(n, d, (n/d)^n*binomial(d+2, 2));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 13 2023
STATUS
approved