A030980 - OEIS

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A030980

Number of planted noncrossing bushes with n nodes; i.e. rooted noncrossing trees with n nodes, root degree 1 and no nonroot nodes of degree 1.

1, 0, 3, 4, 23, 66, 280, 1030, 4207, 16852, 69747, 289950, 1222540, 5192344, 22239672, 95864902, 415730735, 1812177000, 7936353049, 34901789568, 154067755503, 682428824890, 3032173906692, 13510960371744 (list; graph; refs; listen; history; internal format)

	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-2, k-1), k=1..n)/n; G.f.: satisfies A^3 + 2 z A^3 - 2 A^2 - 4 z A^2 + A + 2 z A - z = 0`
	CROSSREFS	`Sequence in context: A042595 A002351 A042035 * A041861 A042377 A032831` `Adjacent sequences: A030977 A030978 A030979 * A030981 A030982 A030983`
	KEYWORD	`nonn`
	AUTHOR	`Emeric Deutsch (deutsch(AT)duke.poly.edu)`

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Last modified February 17 06:13 EST 2012. Contains 205991 sequences.