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%I #7 Sep 16 2019 12:38:22
%S 1,2,2,3,2,3,2,4,3,3,2,4,2,3,4,5,2,4,2,4,3,3,2,5,3,3,4,4,2,5,2,6,4,3,
%T 4,5,2,3,3,5,2,4,2,4,6,3,2,6,3,4,4,4,2,5,4,5,3,3,2,6,2,3,4,7,3,5,2,4,
%U 4,5,2,6,2,3,6,4,4,4,2,6,5,3,2,5,4,3,3
%N Number of stable divisors of n.
%C 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. A number is stable if its distinct prime indices are pairwise indivisible. Stable numbers are listed in A316476. Maximum stable divisor is A327393.
%H Gus Wiseman, <a href="https://docs.google.com/document/d/e/2PACX-1vSX9dPMGJhxB8rOknCGvOs6PiyhupdWNpqLsnphdgU6MEVqFBnWugAXidDhwHeKqZe_YnUqYeGOXsOk/pub">Sequences counting and encoding certain classes of multisets</a>
%e The stable divisors of 60 are {1, 2, 3, 4, 5, 15}, so a(60) = 6.
%t stableQ[u_,Q_]:=!Apply[Or,Outer[#1=!=#2&&Q[#1,#2]&,u,u,1],{0,1}];
%t Table[Length[Select[Divisors[n],stableQ[PrimePi/@First/@FactorInteger[#],Divisible]&]],{n,100}]
%Y See link for additional cross-references.
%Y Cf. A000005, A033273, A303362.
%K nonn
%O 1,2
%A _Gus Wiseman_, Sep 15 2019
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