OFFSET
1,3
MATHEMATICA
f[1] = {1/2}; f[n_] := f[n] = Union[Flatten[Table[Outer[Power, f[k], f[n - k]], {k, n - 1}]], SameTest -> Equal]; Table[Length[f[n]], {n, 1, 10}] (* Vladimir Reshetnikov, Nov 01 2011 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Vladimir Reshetnikov, Oct 27 2011
EXTENSIONS
a(13)-a(14) from Alois P. Heinz, Feb 20 2013
STATUS
approved