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A158771 a(n)=78*n^2-1. 1
77, 311, 701, 1247, 1949, 2807, 3821, 4991, 6317, 7799, 9437, 11231, 13181, 15287, 17549, 19967, 22541, 25271, 28157, 31199, 34397, 37751, 41261, 44927, 48749, 52727, 56861, 61151, 65597, 70199, 74957, 79871, 84941, 90167, 95549, 101087 (list; graph; refs; listen; history; internal format)
OFFSET

1,1

COMMENTS

The identity (78*n^2-1)^2 - (1521*n^2-39) * (2*n)^2 = 1 can be written as

the Pell equation (a(n))^2 - A158770(n) * (A005843(n))^2 = 1.

LINKS

Edward Everett Withford, Pell Equation

Wolfram MathWorld, Pell Equation

Vincenzo Librandi, X^2-AY^2=1

FORMULA

a(n)= 3*a(n-1) -3*a(n-2) +a(n-3). G.f.: x*(-77-80*x+x^2)/(x-1)^3.

CROSSREFS

Cf. A005843, A158770

Sequence in context: A029558 A156652 A158767 * A020206 A020304 A154058

Adjacent sequences:  A158768 A158769 A158770 * A158772 A158773 A158774

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Mar 26 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 15 21:56 EST 2012. Contains 205860 sequences.