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%I #13 Sep 08 2022 08:45:51
%S 1,1520,4620799,14047227440,42703566796801,129818829015047600,
%T 394649197502177907199,1199733430587791822837360,
%U 3647189234337689639247667201,11087454072653145915521085453680
%N x-values in the solution to x^2-31*y^2=1.
%C The corresponding values of y of this Pell equation are in A174771.
%H Vincenzo Librandi, <a href="/A174746/b174746.txt">Table of n, a(n) for n = 1..200</a>
%H <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (3040,-1).
%F a(n) = 3040*a(n-1)-a(n-2) with a(1)=1, a(2)=1520.
%F G.f.: x*(1-1520*x)/(1-3040*x+x^2).
%t LinearRecurrence[{3040,-1},{1,1520},30]
%o (Magma) I:=[1, 1520]; [n le 2 select I[n] else 3040*Self(n-1)-Self(n-2): n in [1..20]];
%Y Cf. A174771.
%K nonn,easy
%O 1,2
%A _Vincenzo Librandi_, Apr 12 2010
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