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A158689 a(n)=66*n^2+1. 1
1, 67, 265, 595, 1057, 1651, 2377, 3235, 4225, 5347, 6601, 7987, 9505, 11155, 12937, 14851, 16897, 19075, 21385, 23827, 26401, 29107, 31945, 34915, 38017, 41251, 44617, 48115, 51745, 55507, 59401, 63427, 67585, 71875, 76297, 80851, 85537 (list; graph; refs; listen; history; internal format)
OFFSET

0,2

COMMENTS

The identity (66*n^2+1)^2 - (1089*n^2+33) * (2*n)^2 = 1 can be written as

the Pell equation (a(n))^2 - A158688(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)= 3*a(n-1) -3*a(n-2) +a(n-3). G.f.: -(1+64*x+67*x^2)/(x-1)^3.

CROSSREFS

Cf. A005843, A158688

Sequence in context: A142273 A141985 A142429 * A142486 A158730 A140731

Adjacent sequences:  A158686 A158687 A158688 * A158690 A158691 A158692

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Mar 24 2009

EXTENSIONS

Comment rewritten, a(0) added and formula replaced by R. J. Mathar, (mathar(AT)strw.leidenuniv.nl), Oct 22 2009

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Last modified February 17 07:41 EST 2012. Contains 205998 sequences.