OFFSET
1,1
COMMENTS
The multiplicative order of a mod m, gcd(a,m)=1, is the smallest natural number d for which a^d = 1 (mod m). a(n) = number of orders of degree-n monic irreducible polynomials over GF(5).
Also, number of primitive factors of 5^n - 1 (cf. A218357). - Max Alekseyev, May 03 2022
LINKS
Max Alekseyev, Table of n, a(n) for n = 1..502
FORMULA
MAPLE
with(numtheory):
a:= n-> add(mobius(n/d)*tau(5^d-1), d=divisors(n)):
seq(a(n), n=1..50); # Alois P. Heinz, Oct 12 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladeta Jovovic, Feb 06 2001
STATUS
approved