id:A158500 - OEIS Search Results

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Expansion of (1+sqrt(1+4x))*(1+2x)/(2*sqrt(1+4x)).

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1, 1, 1, -4, 15, -56, 210, -792, 3003, -11440, 43758, -167960, 646646, -2496144, 9657700, -37442160, 145422675, -565722720, 2203961430, -8597496600, 33578000610, -131282408400, 513791607420, -2012616400080 (list; graph; listen)

	OFFSET	`0,4`
	COMMENT	`Hankel transform is A158501. Row sums of the Riordan array` `((1+2x)/sqrt(1+4x), xc(-x^2))=((1-x^2)/(1+x^2),x/(1-x)^2)^{-1}, where c(x) is the g.f. of A000108.`
	FORMULA	`a(n)=C(1,n)+(-1)^n*C(2n-2,n-2).`
	CROSSREFS	`Cf. A001791.` `Sequence in context: A125905 A026030 A047038 this_sequence A001791 A047128 A087438` `Adjacent sequences: A158497 A158498 A158499 this_sequence A158501 A158502 A158503`
	KEYWORD	`easy,sign`
	AUTHOR	`Paul Barry (pbarry(AT)wit.ie), Mar 20 2009`

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.

AT&T Labs Research