OFFSET
0,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..400
FORMULA
a(n) = Sum_{d|n} 7^d * mu(n/d) for n>0, a(0) = 1.
G.f.: 1 + 7 * Sum_{k>=1} mu(k) * x^k / (1 - 7*x^k). - Ilya Gutkovskiy, Apr 14 2021
MAPLE
with(numtheory):
a:= n-> `if`(n=0, 1, add(7^d *mobius(n/d), d=divisors(n))):
seq(a(n), n=0..30);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Oct 21 2012
STATUS
approved