OFFSET
0,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..100
FORMULA
a(n) = Sum_{d|n} phi(n/d)*(5*d)!/(d!^5*5*n) if n>0 and a(0) = 1.
a(n) ~ 5^(5*n-1/2) / (4 * Pi^2 * n^3). - Vaclav Kotesovec, Aug 23 2015
EXAMPLE
a(0) = 1: the empty necklace.
a(1) = 24: {01234, 01243, ..., 04321}.
MAPLE
with(numtheory):
a:= n-> `if`(n=0, 1, add(phi(n/d) * (5*d)!/(d!^5 *5*n), d=divisors(n))):
seq(a(n), n=0..14);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Feb 24 2012
STATUS
approved