OFFSET
1,6
LINKS
EXAMPLE
The a(9) = 8 locally stable rooted identity trees:
((((((((o))))))))
(((((o)((o))))))
((((o)(((o))))))
(((o)((((o))))))
((((o))(((o)))))
((o)(((((o))))))
((o)((o)((o))))
(((o))((((o)))))
MATHEMATICA
strut[n_]:=strut[n]=If[n===1, {{}}, Select[Join@@Function[c, Union[Sort/@Tuples[strut/@c]]]/@IntegerPartitions[n-1], UnsameQ@@#&&Select[Tuples[#, 2], UnsameQ@@#&&Complement@@#=={}&]=={}&]];
Table[Length[strut[n]], {n, 20}]
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Gus Wiseman, Jul 04 2018
STATUS
approved