A158679 - OEIS

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A158679

a(n)=31*(31*n^2-1).

930, 3813, 8618, 15345, 23994, 34565, 47058, 61473, 77810, 96069, 116250, 138353, 162378, 188325, 216194, 245985, 277698, 311333, 346890, 384369, 423770, 465093, 508338, 553505, 600594, 649605, 700538, 753393, 808170, 864869, 923490, 984033 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,1`
	COMMENTS	`The identity (62n^2-1)^2 - (961n^2-31) * (2n)^2 = 1 can be written as` `the Pell equation (A158680(n))^2 - a(n) (A005843(n))^2 = 1.`
	LINKS	`Philippe Chevanne, Pell Equation` `Vincenzo Librandi, X^2-AY^2=1` `Wolfram MathWorld, Pell Equation`
	FORMULA	`a(n)= 3a(n-1) -3a(n-2) +a(n-3). G.f.: 31x(-30-33*x+x^2)/(x-1)^3.`
	CROSSREFS	`Cf. A005843, A158680` `Sequence in context: A068651 A175726 A115958 * A035856 A093231 A105213` `Adjacent sequences: A158676 A158677 A158678 * A158680 A158681 A158682`
	KEYWORD	`nonn,easy`
	AUTHOR	`Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Mar 24 2009`
	EXTENSIONS	`Comment rewritten and formula replaced by R. J. Mathar, (mathar(AT)strw.leidenuniv.nl), Oct 22 2009`

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Last modified February 18 00:14 EST 2012. Contains 206085 sequences.