OFFSET
1,3
FORMULA
a(n) = Sum_{d|n} binomial(d+n/d-2,d).
If p is prime, a(p) = p - 1.
PROG
(PARI) a(n) = sumdiv(n, d, binomial(d+n/d-2, d));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Oct 30 2023
STATUS
approved