2,5

If a,b are binary trees, a.b is equal to tree b where a copy of a is put on each of b's external node. This is non-commutative but associative. A binary tree a is prime if it is different from the 1 node tree and if a=b.c implies that b or c is equal to the 1 node tree.

Index entries for sequences related to rooted trees

A035010(n)+A035102(n)=Catalan(n-1)=A000108(n-1).

Cf. A035010.

Adjacent sequences: A035099 A035100 A035101 this_sequence A035103 A035104 A035105

Sequence in context: A133844 A016683 A100074 this_sequence A021248 A098487 A019127

nonn

Bernard AMERLYNCK (B.Amerlynck(AT)ulg.ac.be)