A174746 x-values in the solution to x^2-31*y^2=1.

1, 1520, 4620799, 14047227440, 42703566796801, 129818829015047600, 394649197502177907199, 1199733430587791822837360, 3647189234337689639247667201, 11087454072653145915521085453680

Offset

1,2

Comments

The corresponding values of y of this Pell equation are in A174771.

Links

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

Index entries for linear recurrences with constant coefficients, signature (3040,-1).

Formula

a(n) = 3040*a(n-1)-a(n-2) with a(1)=1, a(2)=1520.

G.f.: x*(1-1520*x)/(1-3040*x+x^2).

Mathematica

LinearRecurrence[{3040, -1}, {1, 1520}, 30]

Prog

(Magma) I:=[1, 1520]; [n le 2 select I[n] else 3040*Self(n-1)-Self(n-2): n in [1..20]];

Crossrefs

Cf. A174771.

Sequence in context: A203386 A157375 A331659 * A074906 A307745 A025413

Adjacent sequences: A174743 A174744 A174745 * A174747 A174748 A174749

Keyword

nonn,easy

Author

Vincenzo Librandi, Apr 12 2010

Status

approved