OFFSET
1,2
COMMENTS
PROG
(PARI) is(n) = { my (v=-1); forprime (p=2, oo, if (n==1, return (1), v==v=valuation(n, p), return (0), n\=p^v)) }
CROSSREFS
KEYWORD
nonn
AUTHOR
Rémy Sigrist, Jul 23 2022
STATUS
approved