A131721 - OEIS

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A131721

Overlay of Pell companion numbers: a(n)=A001333(n)+A001333(n-6).

1, 1, 3, 7, 17, 41, 100, 240, 580, 1400, 3380, 8160, 19700, 47560, 114820, 277200, 669220, 1615640, 3900500, 9416640, 22733780, 54884200, 132502180, 319888560, 772279300, 1864447160, 4501173620, 10866794400, 26234762420, 63336319240 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,3`
	LINKS	`Index to sequences with linear recurrences with constant coefficients, signature (2,1)`
	FORMULA	`a(n) = A001333(n), n<6. a(n) = A001333(n)+A001333(n-6) = 20*A000129(n-3), n>=6.` `O.g.f.: (x-1)(x^2+1)(x^4-x^2+1)/(-1+2x+x^2). - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 16 2008`
	CROSSREFS	`Cf. A131710.` `Sequence in context: A123335 A089742 A187258 * A058351 A175094 A086395` `Adjacent sequences: A131718 A131719 A131720 * A131722 A131723 A131724`
	KEYWORD	`nonn,easy`
	AUTHOR	`Paul Curtz (bpcrtz(AT)free.fr), Sep 15 2007`
	EXTENSIONS	`Edited and extended by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 16 2008`

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Last modified February 17 14:19 EST 2012. Contains 206038 sequences.