This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
Sequence of trees begins: 1 o 2 (o) 3 ((o)) 5 (((o))) 6 (o(o)) 10 (o((o))) 11 ((((o)))) 15 ((o)((o))) 22 (o(((o)))) 26 (o(o(o))) 30 (o(o)((o))) 31 (((((o))))) 33 ((o)(((o)))) 39 ((o)(o(o))) 55 (((o))(((o)))) 58 (o(o((o)))) 62 (o((((o))))) 65 (((o))(o(o))) 66 (o(o)(((o)))) 78 (o(o)(o(o))) 87 ((o)(o((o)))) 93 ((o)((((o))))) 94 (o((o)((o))))
MGtree[n_]:=If[n===1,{},MGtree/@Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
idthinQ[t_]:=And@@Cases[t,b_List:>UnsameQ@@b&&Length[b]>=Max@@Length/@b,{0,Infinity}];
Select[Range[500],idthinQ[MGtree[#]]&]
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