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A157949
a(n) = 128*n - 1.
2
127, 255, 383, 511, 639, 767, 895, 1023, 1151, 1279, 1407, 1535, 1663, 1791, 1919, 2047, 2175, 2303, 2431, 2559, 2687, 2815, 2943, 3071, 3199, 3327, 3455, 3583, 3711, 3839, 3967, 4095, 4223, 4351, 4479, 4607, 4735, 4863, 4991, 5119, 5247, 5375, 5503
OFFSET
1,1
COMMENTS
The identity (128*n-1)^2 - (64*n^2-n)*(16)^2 = 1 can be written as a(n)^2 - A157948(n)*(16)^2 = 1. - Vincenzo Librandi, Jan 29 2012
LINKS
E. J. Barbeau, Polynomial Excursions, Chapter 10:Diophantine equations (2010), pages 84-85 (row 14 in the first table at p. 85, case d(t) = t*(8^2*t-1)).
Vincenzo Librandi, X^2-AY^2=1 [broken link]
FORMULA
a(n) = 2*a(n-1) - a(n-2). - Vincenzo Librandi, Jan 29 2012
G.f.: x*(127+x)/(1-x)^2. - Vincenzo Librandi, Jan 29 2012
PROG
(PARI) for(n=1, 40, print1(128*n - 1", ")); \\ Vincenzo Librandi, Jan 29 2012
CROSSREFS
Cf. A157948.
Sequence in context: A276495 A196657 A138127 * A142165 A031933 A283622
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Mar 10 2009
STATUS
approved