A322075 Number of factorizations of n into nonprime squarefree numbers > 1.

1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1, 1, 1, 1, 0, 1, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 0, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 1, 1, 1, 1

Offset

1,210

Comments

First term greater than 1 is a(210) = 4.

Links

G. C. Greubel, Table of n, a(n) for n = 1..10000

Example

The a(420) = 3 factorizations: (6*70), (10*42), (14*30).

Mathematica

sqnopfacs[n_]:=If[n<=1, {{}}, Join@@Table[Map[Prepend[#, d]&, Select[sqnopfacs[n/d], Min@@#>=d&]], {d, Select[Rest[Divisors[n]], !PrimeQ[#]&&SquareFreeQ[#]&]}]]
Table[Length[sqnopfacs[n]], {n, 100}]

Crossrefs

Cf. A000469, A001055, A001221, A001222, A005117, A007716, A318871, A318953, A320655, A320656, A320658, A320659.

Sequence in context: A339661 A320656 A354819 * A369255 A288220 A173856

Adjacent sequences: A322072 A322073 A322074 * A322076 A322077 A322078

Keyword

nonn

Author

Gus Wiseman, Nov 25 2018

Status

approved