OFFSET
1,2
EXAMPLE
Sequence of trees begins:
1 o
2 (o)
3 ((o))
5 (((o)))
6 (o(o))
7 ((oo))
10 (o((o)))
11 ((((o))))
13 ((o(o)))
14 (o(oo))
15 ((o)((o)))
17 (((oo)))
19 ((ooo))
21 ((o)(oo))
22 (o(((o))))
23 (((o)(o)))
26 (o(o(o)))
29 ((o((o))))
30 (o(o)((o)))
MATHEMATICA
nn=500;
primeMS[n_]:=If[n===1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
MGweight[n_]:=If[n===1, 1, 1+Total[MGweight/@primeMS[n]]];
Select[Range[nn], UnsameQ@@MGweight/@primeMS[#]&]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Jan 21 2018
STATUS
approved