id:A117381 - OEIS Search Results

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Expansion of 1/((1-4*x*c(x))(1-x^2*c(x))), c(x) the g.f. of A000108.

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1, 4, 21, 109, 575, 3047, 16192, 86171, 458972, 2445825, 13037508, 69509558, 370634265, 1976421031, 10539858413, 56208784808, 299766435277, 1598704176149, 8526238418811, 45472594256564, 242517996824355 (list; graph; listen)

	OFFSET	`0,2`
	COMMENT	`Diagonal sums of number triangle A117380.`
	FORMULA	`a(n)=sum{k=0..floor(n/2), [k<=n-k]sum{j=0..n-k, (j/(n-k-j))C(2n-k-j,n-k-j)[k<=j]*4^(j-k)}}`
	CROSSREFS	`Sequence in context: A015531 A083425 A100237 this_sequence A010908 A136786 A026335` `Adjacent sequences: A117378 A117379 A117380 this_sequence A117382 A117383 A117384`
	KEYWORD	`easy,nonn`
	AUTHOR	`Paul Barry (pbarry(AT)wit.ie), Mar 10 2006`

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Last modified November 29 12:46 EST 2009. Contains 167659 sequences.

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