A174767 y-values in the solution to x^2 - 23*y^2 = 1.

0, 5, 240, 11515, 552480, 26507525, 1271808720, 61020311035, 2927703120960, 140468729495045, 6739571312641200, 323358954277282555, 15514490233996921440, 744372172277574946565, 35714349779089600513680

Offset

1,2

Comments

The corresponding values of x of this Pell equation are in A114051.

Links

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

Index entries for linear recurrences with constant coefficients, signature (48,-1).

Formula

a(n) = 48*a(n-1)-a(n-2) with a(1)=0, a(2)=5.

G.f.: 5*x^2/(1-48*x+x^2).

Mathematica

LinearRecurrence[{48, -1}, {0, 5}, 30]

Prog

(Magma) I:=[0, 5]; [n le 2 select I[n] else 48*Self(n-1)-Self(n-2): n in [1..20]];

Crossrefs

Cf. A114051.

Sequence in context: A269551 A200962 A270052 * A230885 A142732 A242625

Adjacent sequences: A174764 A174765 A174766 * A174768 A174769 A174770

Keyword

nonn,easy

Author

Vincenzo Librandi, Apr 14 2010

Status

approved