id:A158645 - OEIS Search Results

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a(n)=27*(27*n^2+1).

+0
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27, 756, 2943, 6588, 11691, 18252, 26271, 35748, 46683, 59076, 72927, 88236, 105003, 123228, 142911, 164052, 186651, 210708, 236223, 263196, 291627, 321516, 352863, 385668, 419931, 455652, 492831, 531468, 571563, 613116, 656127, 700596, 746523 (list; graph; listen)

	OFFSET	`0,1`
	COMMENT	`The identity (54n^2+1)^2 - (729n^2+27) * (2n)^2 = 1 can be written as` `the Pell equation (A158646(n))^2 - a(n) (A005843(n))^2 =1.`
	LINKS	`Vincenzo Librandi, X^2-AY^2=1` `Edward Everett Withford, Pell Equation` `Wolfram MathWorld, Pell Equation`
	CROSSREFS	`a(n)= 3a(n-1) -3a(n-2) +a(n-3). G.f.: -27(1+25x+28*x^2)/(x-1)^3.` `Cf. A005843, A158646` `Sequence in context: A046240 A042406 A159668 this_sequence A138979 A159234 A120715` `Adjacent sequences: A158642 A158643 A158644 this_sequence A158646 A158647 A158648`
	KEYWORD	`nonn,easy`
	AUTHOR	`Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Mar 23 2009`
	EXTENSIONS	`Comment rephrased and redundant formula replaced by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 19 2009`

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Last modified December 16 17:18 EST 2009. Contains 170825 sequences.

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