OFFSET
1,4
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..22001
FORMULA
EXAMPLE
For n=25, with divisors [1, 5, 25], both B(5,x) and B(25,x) are irreducible, so only 1 is counted and a(25)=1.
PROG
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Nov 10 2017
STATUS
approved