OFFSET
1,3
COMMENTS
LINKS
EXAMPLE
The divisors of 90 that are 1 or whose prime indices have a common divisor > 1 are {1, 3, 5, 9}, so a(90) = 9.
MATHEMATICA
Table[Max[Select[Divisors[n], GCD@@PrimePi/@First/@FactorInteger[#]!=1&]], {n, 100}]
PROG
(PARI) A327656(n) = vecmax(select(d -> (1==d)||(gcd(apply(primepi, factor(d)[, 1]~))>1), divisors(n))); \\ Antti Karttunen, Dec 06 2021
CROSSREFS
The union consists of {1} followed by A318978.
See link for additional cross-references.
KEYWORD
nonn
AUTHOR
Gus Wiseman, Sep 21 2019
STATUS
approved