|
%I #15 Jan 17 2024 05:23:10
%S 13,26403,53598077,108804069907,220872208313133,448370474071590083,
%T 910191841493119555357,1847688989860558625784627,
%U 3750807739225092517223237453,7614137862937947949404546244963,15456696110956295112198711654037437
%N Numbers Y such that 381*Y^2+127 is a square.
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2030,-1).
%F a(n+2) = 2030*a(n+1)-a(n).
%F G.f.: 13*x*(x+1) / (x^2-2030*x+1). - _Colin Barker_, Oct 21 2014
%e a(1)=13 because the first relation is 254^2=381*13^2+127.
%t LinearRecurrence[{2030, -1}, {13, 26403}, 15] (* _Paolo Xausa_, Jan 17 2024 *)
%o (PARI) Vec(13*x*(x+1)/(x^2-2030*x+1) + O(x^20)) \\ _Colin Barker_, Oct 21 2014
%K easy,nonn
%O 1,1
%A _Richard Choulet_, Oct 16 2008
%E Editing and a(11) from _Colin Barker_, Oct 21 2014
| 