id:A030981 - OEIS Search Results

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Noncrossing bushes with n nodes; i.e. rooted noncrossing trees with n nodes and no nonroot nodes of degree 1.

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1, 1, 4, 11, 41, 146, 564, 2199, 8835, 35989, 148912, 623008, 2633148, 11222160, 48181056, 208180847, 904593623, 3950338043, 17328256180, 76316518987, 337332601513, 1495992837550, 6654367576732, 29681131861564 (list; graph; listen)

	OFFSET	`1,3`
	LINKS	`Index entries for sequences related to rooted trees`
	FORMULA	`Sum((-1)^(n-k)2^(n-k)binomial(n, k)binomial(3k, k-1), k=1..n)/n; G.f. satisfies z A^3 + 3 z A^2 + z A - A + z = 0`
	CROSSREFS	`Sequence in context: A121096 A047091 A121092 this_sequence A000296 A032265 A110143` `Adjacent sequences: A030978 A030979 A030980 this_sequence A030982 A030983 A030984`
	KEYWORD	`nonn`
	AUTHOR	`Emeric Deutsch (deutsch(AT)duke.poly.edu)`

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Last modified August 29 17:54 EDT 2008. Contains 143238 sequences.

AT&T Labs Research