OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..1000
EXAMPLE
The a(3) = 5 trees: (o(o(oo))), (o(oooo)), ((oo)(oo)), (ooo(oo)), (oooooo).
MATHEMATICA
erut[n_]:=erut[n]=If[n===1, {{}}, Join@@Function[c, Union[Sort/@Tuples[erut/@c]]]/@Select[IntegerPartitions[n-1], EvenQ[Length[#]]&]];
Table[Length[erut[n]], {n, 1, 30, 2}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Jan 13 2018
STATUS
approved