id:A108489 - OEIS Search Results

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Expansion of 1/sqrt(1-2x-5x^2-6x^3+9x^4).

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1, 1, 4, 13, 37, 130, 427, 1441, 4954, 16987, 58843, 204610, 713893, 2500183, 8778478, 30898309, 108987427, 385136680, 1363252603, 4832572951, 17153677534, 60961916965, 216887253409, 772400234074, 2753261490919, 9822393082513 (list; graph; listen)

	OFFSET	`0,3`
	COMMENT	`In general, sum{k=0..n, C(n-k,k)^2a^kb^(n-k)} has expansion 1/sqrt(1-2bx-(2ab-b^2)x^2-2ab^2x^3+(ab)^2*x^4).`
	FORMULA	`a(n)=sum{k=0..n, C(n-k, k)^2*3^k}`
	CROSSREFS	`Cf. A108484.` `Adjacent sequences: A108486 A108487 A108488 this_sequence A108490 A108491 A108492` `Sequence in context: A077842 A067633 A091874 this_sequence A024450 A047094 A089092`
	KEYWORD	`easy,nonn`
	AUTHOR	`Paul Barry (pbarry(AT)wit.ie), Jun 04 2005`

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Last modified October 7 14:39 EDT 2008. Contains 144666 sequences.

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