A176377 x-values in the solution to x^2-70*y^2=1.

1, 251, 126001, 63252251, 31752504001, 15939693756251, 8001694513134001, 4016834705899512251, 2016443020667042016001, 1012250379540149192520251, 508147674086134227603150001, 255089120140859842107588780251

Offset

1,2

Comments

The corresponding values of y of this Pell equation are in A176378.

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..200

Index entries for linear recurrences with constant coefficients, signature (502,-1).

Formula

a(n) = 502*a(n-1)-a(n-2) with a(1)=1, a(2)=251.

G.f.: x*(1-251*x)/(1-502*x+x^2). - Harvey P. Dale, Jun 14 2011

Mathematica

LinearRecurrence[{502, -1}, {1, 251}, 20] (* or *) CoefficientList[ Series[ (1-251 x)/(1-502 x+x^2), {x, 0, 20}], x] (* Harvey P. Dale, Jun 14 2011 *)

Prog

(PARI) Vec((1-251*x)/(1-502*x+x^2)+O(x^99)) \\ Charles R Greathouse IV, Jun 14 2011
(Magma) I:=[1, 251]; [n le 2 select I[n] else 502*Self(n-1)-Self(n-2): n in [1..20]];

Crossrefs

Sequence in context: A365468 A052239 A089236 * A268848 A365917 A365916

Adjacent sequences: A176374 A176375 A176376 * A176378 A176379 A176380

Keyword

nonn,easy

Author

Vincenzo Librandi, Apr 16 2010

Extensions

Definition rewritten and g.f. adapted to the offset from Bruno Berselli, Dec 15 2011

Status

approved