OFFSET
1,4
LINKS
EXAMPLE
The a(8) = 17 locally identity chain trees:
(((((((o))))))) (((((o(o)))))) (((o(o(o))))) (o(o(o(o))))
((((o((o)))))) ((o((o(o))))) (o(o)(o(o)))
(((o(((o)))))) ((o(o((o)))))
((o((((o)))))) (((o)(o(o))))
(o(((((o)))))) (o(((o(o)))))
(o((o((o)))))
(o(o(((o)))))
((o)(o((o))))
(((o))(o(o)))
MATHEMATICA
submultisetQ[M_, N_]:=Or[Length[M]==0, MatchQ[{Sort[List@@M], Sort[List@@N]}, {{x_, Z___}, {___, x_, W___}}/; submultisetQ[{Z}, {W}]]];
idchnplane[n_]:=If[n==1, {{}}, Join@@Table[Select[Tuples[idchnplane/@c], And[UnsameQ@@#, And@@submultisetQ@@@Partition[#, 2, 1]]&], {c, Join@@Permutations/@IntegerPartitions[n-1]}]];
Table[Length[idchnplane[n]], {n, 10}]
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Gus Wiseman, Sep 17 2018
STATUS
approved