OFFSET
1,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = tau(n^9-1)-tau(n^3-1), with tau = A000005.
MAPLE
with(numtheory):
a:= n-> add(mobius(9/d) *tau(n^d-1), d={3, 9}):
seq(a(n), n=1..80);
MATHEMATICA
Table[DivisorSigma[0, n^9-1]-DivisorSigma[0, n^3-1], {n, 70}] (* Harvey P. Dale, Mar 15 2018 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Oct 24 2012
STATUS
approved