A127897 - OEIS

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A127897

Series reversion of x/(1+2x+3x^2+x^3).

0, 1, 2, 7, 27, 114, 507, 2342, 11125, 54002, 266684, 1335610, 6767477, 34629709, 178701317, 928903447, 4859345882, 25563551782, 135153617840, 717740916202, 3826894116962, 20478451476328, 109945087353190 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,3`
	COMMENTS	`Series reversion of A127896.`
	FORMULA	`G.f.: 2sqrt(3)sqrt((1+x)/x)sin(asin(3sqrt(3)/(2sqrt((1+x)/x)))/3)/3; a(n)=sum{k=0..n-1, sum{j=0..k, (1/(2k+j-1))C(n-1,3k-j)C(3k-j,k)C(k,j)2^(n-3k+j-1)3^j}};`
	CROSSREFS	`Sequence in context: A150627 A150628 A106225 * A180473 A154108 A011965` `Adjacent sequences: A127894 A127895 A127896 * A127898 A127899 A127900`
	KEYWORD	`easy,nonn`
	AUTHOR	`Paul Barry (pbarry(AT)wit.ie), Feb 04 2007`

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Last modified February 15 10:56 EST 2012. Contains 205763 sequences.