id:A099515 - OEIS Search Results

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Row sums of triangle A099514, so that a(n) = Sum_{k=0..n} coefficient of z^k in (1 + z + 2*z^2)^(n-[k/2]), where [k/2] is the integer floor of k/2.

+0
2

1, 2, 5, 13, 31, 78, 190, 469, 1150, 2825, 6933, 17015, 41754, 102454, 251393, 616826, 1513453, 3713389, 9111087, 22354678, 54848638, 134574493, 330186518, 810131889, 1987705301, 4876948743, 11965871650, 29358946070, 72033839657 (list; graph; listen)

	OFFSET	`0,2`
	FORMULA	`G.f.: (1-2x^2)/(1-2x-3x^2+3x^3+4*x^4).`
	PROGRAM	`(PARI) a(n)=sum(k=0, n, polcoeff((1+x+2x^2+xO(x^k))^(n-k\2), k))`
	CROSSREFS	`Cf. A099514.` `Sequence in context: A068739 A063636 A076501 this_sequence A056367 A082733 A095134` `Adjacent sequences: A099512 A099513 A099514 this_sequence A099516 A099517 A099518`
	KEYWORD	`nonn`
	AUTHOR	`Paul D. Hanna (pauldhanna(AT)juno.com), Oct 21 2004`

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Last modified September 8 08:06 EDT 2008. Contains 143486 sequences.

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