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 A327657 Number of divisors of n that are 1 or whose prime indices have a common divisor > 1. 0
 1, 1, 2, 1, 2, 2, 2, 1, 3, 2, 2, 2, 2, 2, 3, 1, 2, 3, 2, 2, 4, 2, 2, 2, 3, 2, 4, 2, 2, 3, 2, 1, 3, 2, 3, 3, 2, 2, 4, 2, 2, 4, 2, 2, 4, 2, 2, 2, 3, 3, 3, 2, 2, 4, 3, 2, 4, 2, 2, 3, 2, 2, 6, 1, 4, 3, 2, 2, 3, 3, 2, 3, 2, 2, 4, 2, 3, 4, 2, 2, 5, 2, 2, 4, 3, 2, 4 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798. Numbers whose prime indices have a common divisor > 1 are listed in A318978. 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) = 4. MATHEMATICA Table[Length[Select[Divisors[n], GCD@@PrimePi/@First/@FactorInteger[#]!=1&]], {n, 100}] CROSSREFS See link for additional cross-references. Cf. A000005, A056239, A112798, A281116, A289509, A327406. Sequence in context: A023588 A175242 A225843 * A301957 A318874 A001227 Adjacent sequences:  A327654 A327655 A327656 * A327658 A327659 A327660 KEYWORD nonn AUTHOR Gus Wiseman, Sep 21 2019 STATUS approved

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Last modified August 2 02:40 EDT 2021. Contains 346409 sequences. (Running on oeis4.)