OFFSET
1,1
COMMENTS
Warning: I have only confirmed the first eight terms. The rest are derived from A045782. - Gus Wiseman, Jan 07 2020
LINKS
R. E. Canfield, P. Erdős and C. Pomerance, On a Problem of Oppenheim concerning "Factorisatio Numerorum", J. Number Theory 17 (1983), 1-28.
MATHEMATICA
nn=15;
fam[n_]:=fam[n]=If[n<=1, {{}}, Join@@Table[Map[Prepend[#, d]&, Select[fam[n/d], Min@@#>=d&]], {d, Rest[Divisors[n]]}]];
nds=Length/@Array[fam[#]&, 2^nn];
Complement[Range[nn], nds]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Jan 07 2020
STATUS
approved