id:A158598 - OEIS Search Results

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a(n)=40*n^2-1.

+0
2

39, 159, 359, 639, 999, 1439, 1959, 2559, 3239, 3999, 4839, 5759, 6759, 7839, 8999, 10239, 11559, 12959, 14439, 15999, 17639, 19359, 21159, 23039, 24999, 27039, 29159, 31359, 33639, 35999, 38439, 40959, 43559, 46239, 48999, 51839, 54759 (list; graph; listen)

	OFFSET	`1,1`
	COMMENT	`The identity (40n^2-1)^2 - (400n^2-20)(2n)^2 = 1 can be written in` `Pell-format as (a(n))^2 - A158597(n)* (A005843(n))^2 =1.`
	LINKS	`Vincenzo Librandi, X^2-AY^2=1` `Edward Everett Withford, Pell Equation` `Wolfram MathWorld, Pell Equation`
	FORMULA	`a(n)= 3a(n-1) -3a(n-2) +a(n-3). G.f.: x(-39-42x+x^2)/(x-1)^3.`
	CROSSREFS	`Cf. A005843, A158597` `Sequence in context: A072253 A128826 A158593 this_sequence A105838 A124619 A068975` `Adjacent sequences: A158595 A158596 A158597 this_sequence A158599 A158600 A158601`
	KEYWORD	`nonn,easy`
	AUTHOR	`Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Mar 22 2009`
	EXTENSIONS	`Comment rewritten, formula replaced by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 28 2009`

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Last modified November 27 22:38 EST 2009. Contains 167602 sequences.

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