A174751 x-values in the solution to x^2-39*y^2=1.

1, 25, 1249, 62425, 3120001, 155937625, 7793761249, 389532124825, 19468812480001, 973051091875225, 48633085781281249, 2430681237972187225, 121485428812828080001, 6071840759403431812825, 303470552541358762561249

Offset

1,2

Comments

The corresponding values of y of this Pell equation are in A174776.

Links

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

Index entries for linear recurrences with constant coefficients, signature (50,-1).

Formula

a(n) = 50*a(n-1)-a(n-2) with a(1)=1, a(2)=25.

G.f.: x*(1-25*x)/(1-50*x+x^2).

Mathematica

LinearRecurrence[{50, -1}, {1, 25}, 30]
Rest[CoefficientList[Series[x (1-25x)/(1-50x+x^2), {x, 0, 20}], x]] (* Harvey P. Dale, Aug 10 2021 *)

Prog

(Magma) I:=[1, 25]; [n le 2 select I[n] else 50*Self(n-1)-Self(n-2): n in [1..20]];

Crossrefs

Cf. A174776.

Sequence in context: A012851 A181719 A096330 * A042203 A042200 A104593

Adjacent sequences: A174748 A174749 A174750 * A174752 A174753 A174754

Keyword

nonn,easy

Author

Vincenzo Librandi, Apr 13 2010

Status

approved