A303708 - OEIS

A303708

Number of aperiodic factorizations of n using elements of A007916 (numbers that are not perfect powers).

0, 1, 1, 0, 1, 2, 1, 0, 0, 2, 1, 3, 1, 2, 2, 0, 1, 3, 1, 3, 2, 2, 1, 4, 0, 2, 0, 3, 1, 5, 1, 0, 2, 2, 2, 3, 1, 2, 2, 4, 1, 5, 1, 3, 3, 2, 1, 5, 0, 3, 2, 3, 1, 4, 2, 4, 2, 2, 1, 9, 1, 2, 3, 0, 2, 5, 1, 3, 2, 5, 1, 8, 1, 2, 3, 3, 2, 5, 1, 5, 0, 2, 1, 9, 2, 2, 2, 4, 1, 9, 2

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OFFSET

1,6

COMMENTS

An aperiodic factorization of n is a finite multiset of positive integers greater than 1 whose product is n and whose multiplicities are relatively prime.

The positions of zeros in this sequence are the prime powers A000961.

LINKS

Table of n, a(n) for n=1..91.

FORMULA

a(n) = Sum_{d in A007916, d|A052409(n)} mu(d) * A303707(n^(1/d)).

EXAMPLE

The a(144) = 8 aperiodic factorizations are (2*2*2*3*6), (2*2*2*18), (2*2*3*12), (2*3*24), (2*6*12), (2*72), (3*48) and (6*24). Missing from this list are (12*12), (2*2*6*6) and (2*2*2*2*3*3).

MATHEMATICA

radQ[n_]:=Or[n===1, GCD@@FactorInteger[n][[All, 2]]===1];

facsr[n_]:=If[n<=1, {{}}, Join@@Table[Map[Prepend[#, d]&, Select[facsr[n/d], Min@@#>=d&]], {d, Select[Rest[Divisors[n]], radQ]}]];

Table[Length[Select[facsr[n], GCD@@Length/@Split[#]===1&]], {n, 100}]

CROSSREFS

Cf. A000740, A000837, A001055, A001597, A007716, A007916, A052409, A052410, A100953, A275870, A281116, A301700, A303386, A303431, A303546, A303551, A303707, A303709, A303710.

Sequence in context: A180026 A136176 A291914 * A319138 A349396 A330462

Adjacent sequences: A303705 A303706 A303707 * A303709 A303710 A303711

KEYWORD

nonn

AUTHOR

Gus Wiseman, Apr 29 2018

STATUS

approved