OFFSET
1,2
COMMENTS
Dirichlet convolution of mu(n) with 9^(n-1).
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..1048
FORMULA
a(n) = Sum_{d|n} 9^(d-1) * mu(n/d).
a(n) = 9^(n-1) - Sum_{d<n,d|n} a(d).
a(n) = A143325(n,9).
a(n) = A074650(n,9) * n/9.
a(n) = A143324(n,9) / 9.
G.f.: Sum_{k>=1} mu(k)*x^k/(1 - 9*x^k). - Ilya Gutkovskiy, Oct 25 2018
MAPLE
a:= n-> add(`if`(d=n, 9^(n-1), -a(d)), d=numtheory[divisors](n)):
seq(a(n), n=1..25);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Oct 05 2018
STATUS
approved