A128057 - OEIS

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A128057

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

1, 1, -2, -2, 6, 6, -20, -20, 70, 70, -252, -252, 924, 924, -3432, -3432, 12870, 12870, -48620, -48620, 184756, 184756, -705432, -705432, 2704156, 2704156, -10400600, -10400600, 40116600, 40116600, -155117520, -155117520 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,3`
	COMMENTS	`Hankel transform is A128056. Binomial transform is A128058. Unsigned version is A128014.`
	FORMULA	`a(n)=(-1)^C(n,2)(C(n,n/2)(1+(-1)^n)/2+C(n-1,(n-1)/2)*(1-(-1)^n)/2);`
	CROSSREFS	`Sequence in context: A086442 A071407 A109859 * A128014 A135401 A129881` `Adjacent sequences: A128054 A128055 A128056 * A128058 A128059 A128060`
	KEYWORD	`easy,sign`
	AUTHOR	`Paul Barry (pbarry(AT)wit.ie), Feb 13 2007`

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Last modified February 13 08:12 EST 2012. Contains 205451 sequences.