A122918 - OEIS

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A122918

Expansion of (1+x)^2/(1+x+x^2)^2.

1, 0, -2, 2, 1, -4, 3, 2, -6, 4, 3, -8, 5, 4, -10, 6, 5, -12, 7, 6, -14, 8, 7, -16, 9, 8, -18, 10, 9, -20, 11, 10, -22, 12, 11, -24, 13, 12, -26, 14, 13, -28, 15, 14, -30, 16, 15, -32, 17, 16, -34, 18, 17, -36, 19, 18, -38 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,3`
	COMMENTS	`Row sums of Riordan array (1/(1+x+x^2),x/(1+x)^2), A122917.`
	FORMULA	`a(n)=4sqrt(3)cos(2pin/3+pi/6)/9+2(n+1)sin(2pin/3+pi/6)/3; a(n)=sum{k=0..n, A057078(k)A057078(n-k)};`
	CROSSREFS	`Sequence in context: A180228 A197376 A113072 * A177424 A129903 A023616` `Adjacent sequences: A122915 A122916 A122917 * A122919 A122920 A122921`
	KEYWORD	`easy,sign`
	AUTHOR	`Paul Barry (pbarry(AT)wit.ie), Sep 19 2006`

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Last modified February 16 17:48 EST 2012. Contains 205939 sequences.