A175633 Numbers x such that x^2 - 28*y^2 = 1 for some integer y.

1, 127, 32257, 8193151, 2081028097, 528572943487, 134255446617601, 34100354867927167, 8661355881006882817, 2199950293420880308351, 558778713173022591438337, 141927593195654317345029247

Offset: 1

Author

Vincenzo Librandi, Dec 04 2010

Keywords

• nonn

Comments

This sequence gives the values of x in solutions of the Pell equation x^2 - 28*y^2 = 1; the corresponding y values are in A175672. [Edited by Jon E. Schoenfield, May 04 2014]

Links

• Index entries for linear recurrences with constant coefficients, signature (254,-1).

Crossrefs

Cf. A175672.

Row 8 of array A188644.

Formula

a(n) = 254*a(n-1) - a(n-2) (with a(1)=1, a(2)=127).

G.f.: x*(1-127*x)/(1-254*x+x^2). - Bruno Berselli, Apr 18 2011