A054616 a(n) = Sum_{d|n} phi(d)*9^(n/d).

0, 9, 90, 747, 6660, 59085, 532350, 4783023, 43053480, 387422001, 3486843810, 31381059699, 282430082700, 2541865828437, 22876797238470, 205891132215735, 1853020231912080, 16677181699666713, 150094635685484490, 1350851717672992251

Offset: 0

Author

N. J. A. Sloane, Apr 16 2000

Keywords

• nonn

Links

• Seiichi Manyama, Table of n, a(n) for n = 0..1000

Crossrefs

Column k=9 of A185651.

Cf. A054628.

Programs

PARI

a(n) = if(n==0, 0, sumdiv(n, d, eulerphi(d)*9^(n/d))); \\ Altug Alkan, Mar 16 2018

Formula

a(n) = Sum_{k=1..n} 9^gcd(n,k). - Ilya Gutkovskiy, Apr 16 2021