

A327515


Number of steps to reach a fixed point starting with n and repeatedly taking the quotient by the maximum divisor that is 1, 2, or a nonprime number whose prime indices are pairwise coprime (A327512, A327514).


1



0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0
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OFFSET

1


COMMENTS

Positions of zeros are A289509.
First term > 1 is a(225) = 2.
First zero not in A318978 is a(17719) = 0.
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 that are 1, 2, or a nonprime number whose prime indices are pairwise coprime are listed in A302696.


LINKS

Table of n, a(n) for n=1..87.
Gus Wiseman, Sequences counting and encoding certain classes of multisets


FORMULA

a(15^n) = n.


EXAMPLE

We have 50625 > 3375 > 225 > 15 > 1, so a(50625) = 4.


MATHEMATICA

primeMS[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
Table[Length[FixedPointList[#/Max[Select[Divisors[#], #==1CoprimeQ@@primeMS[#]&]]&, n]]2, {n, 100}]


CROSSREFS

See link for additional crossreferences.
Cf. A000005, A006530, A056239, A112798, A289509, A302569, A302696, A304711.
Sequence in context: A188510 A131734 A134452 * A327532 A073445 A285589
Adjacent sequences: A327512 A327513 A327514 * A327516 A327517 A327518


KEYWORD

nonn


AUTHOR

Gus Wiseman, Sep 19 2019


STATUS

approved



