OFFSET
0,2
LINKS
Stefano Spezia, Table of n, a(n) for n = 0..350
FORMULA
a(n) = (1/n)*Sum_{d|n} phi(n/d)*(n+1)^d, for n>0, with a(0)=1.
a(n) is divisible by (n+1); a(n)/(n+1) = A121774(n).
MATHEMATICA
a[0] = 1; a[n_] := DivisorSum[n, (n+1)^# * EulerPhi[n/#] &] / n; Array[a, 20, 0] (* Amiram Eldar, Aug 15 2023 *)
PROG
(PARI) a(n)=if(n==0, 1, (1/n)*sumdiv(n, d, eulerphi(n/d)*(n+1)^d))
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Aug 20 2006
EXTENSIONS
a(18)-a(19) from Amiram Eldar, Aug 15 2023
STATUS
approved