OFFSET
1,8
EXAMPLE
The a(36) = 15 pairs of factorizations:
(2*2*3*3)|(4*9)
(2*2*3*3)|(6*6)
(2*2*3*3)|(36)
(2*2*9)|(6*6)
(2*2*9)|(36)
(2*3*6)|(4*9)
(2*3*6)|(36)
(2*18)|(36)
(3*3*4)|(6*6)
(3*3*4)|(36)
(3*12)|(36)
(4*9)|(6*6)
(4*9)|(36)
(6*6)|(4*9)
(6*6)|(36)
MATHEMATICA
facs[n_]:=If[n<=1, {{}}, Join@@Table[Map[Prepend[#, d]&, Select[facs[n/d], Min@@#>=d&]], {d, Rest[Divisors[n]]}]];
Table[Length[Select[Tuples[facs[n], 2], !Or@@Divisible@@@Tuples[#]&]], {n, 100}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Dec 08 2018
STATUS
approved