A035102 - OEIS

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A035102

Composite binary rooted trees with external nodes.

0, 0, 1, 0, 4, 0, 9, 4, 28, 0, 98, 0, 264, 56, 869, 0, 3016, 0, 9822, 528, 33592, 0, 119530, 196, 416024, 5712, 1486724, 0, 5369336, 0, 19392637, 67184, 70715340, 3696, 259535958, 0 (list; graph; refs; listen; history; internal format)

	OFFSET	`2,5`
	COMMENTS	`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.`
	LINKS	`Index entries for sequences related to rooted trees`
	FORMULA	`A035010(n)+A035102(n)=Catalan(n-1)=A000108(n-1).`
	CROSSREFS	`Cf. A035010.` `Sequence in context: A188777 A016683 A100074 * A187507 A187857 A190262` `Adjacent sequences: A035099 A035100 A035101 * A035103 A035104 A035105`
	KEYWORD	`nonn`
	AUTHOR	`Bernard AMERLYNCK (B.Amerlynck(AT)ulg.ac.be)`

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Last modified February 17 15:44 EST 2012. Contains 206050 sequences.