id:A126220 - OEIS Search Results

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Number of binary trees (i.e. rooted trees where each vertex has either 0,1, or 2 children; and, when only one child is present, it is either a right child or a left child ) with n edges and no adjacent vertices of outdegree 2.

+0
2

1, 2, 5, 14, 40, 116, 344, 1040, 3188, 9880, 30912, 97520, 309856, 990656, 3184672, 10287808, 33379072, 108724864, 355405568, 1165521408, 3833497408, 12642775424, 41799227392, 138512751360, 459973953024, 1530498526208 (list; graph; listen)

	OFFSET	`0,2`
	COMMENT	`a(n)=A126219(n,0), i.e. row 0 of triangle A126219.`
	FORMULA	`G.f.=[1-2z-4z^3-sqrt(1-8z^3+4z^2-4z)]/(8z^4).`
	MAPLE	`g:=(1-4z^3-2z-sqrt(1-8z^3+4z^2-4*z))/8/z^4: gser:=series(g, z=0, 35): seq(coeff(gser, z, n), n=0..30);`
	CROSSREFS	`Cf. A126219.` `Sequence in context: A117189 A052963 A036908 this_sequence A136304 A075496 A114177` `Adjacent sequences: A126217 A126218 A126219 this_sequence A126221 A126222 A126223`
	KEYWORD	`nonn`
	AUTHOR	`Emeric Deutsch (deutsch(AT)duke.poly.edu), Dec 25 2006`

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Last modified August 19 23:53 EDT 2008. Contains 142930 sequences.

AT&T Labs Research