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%I #20 Jan 05 2016 17:04:07
%S 4,13,21,132,837,1373,8708,55229,90597,574596,3644277,5978029,
%T 37914628,240467053,394459317,2501790852,15867181221,26028336893,
%U 165080281604,1046993493533,1717475775621,10892796795012,69085703391957,113327372854093,718759508189188
%N y-values in the solution to 17*x^2 + 16 = y^2.
%C When are both n-1 and 17*n-1 perfect squares? This problem gives the equation 17*x^2+16=y^2.
%H <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,66,0,0,-1).
%F a(n) = 66*a(n-3) - a(n-6), a(1)=4, a(2)=13, a(3)=21, a(4)=132, a(5)=837, a(6)=1373.
%F G.f.: -x*(13*x^5+21*x^4+132*x^3-21*x^2-13*x-4) / (x^6-66*x^3+1). - _Colin Barker_, Sep 01 2013
%e a(7)=66*132-4=8708.
%t LinearRecurrence[{0,0,66,0,0,-1}, {4,13,21,132,837,1373}, 50]
%o (PARI) Vec(-x*(13*x^5+21*x^4+132*x^3-21*x^2-13*x-4)/(x^6-66*x^3+1) + O(x^100)) \\ _Colin Barker_, Sep 01 2013
%Y Cf. A199774, A199772, A199773.
%K nonn,easy
%O 1,1
%A _Sture Sjöstedt_, Nov 10 2011
%E More terms from _T. D. Noe_, Nov 10 2011
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