OFFSET
1,8
COMMENTS
FORMULA
a(2^n) = A002033(n).
EXAMPLE
The a(216) = 4 perfect factorizations:
(2*2*2*3*3*3)
(2*2*2*3*9)
(2*3*3*3*4)
(2*3*4*9)
MATHEMATICA
facs[n_]:=If[n<=1, {{}}, Join@@Table[Map[Prepend[#, d]&, Select[facs[n/d], Min@@#>=d&]], {d, Rest[Divisors[n]]}]];
Table[Length[Select[facs[n], Sort[Times@@@Union[Subsets[#]]]==Divisors[n]&]], {n, 100}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, May 30 2019
STATUS
approved