login
Numbers n such that 2*n^2 + 41 is a square.
0

%I #14 Jul 31 2015 21:06:20

%S 2,8,20,50,118,292,688,1702,4010,9920,23372,57818,136222,336988,

%T 793960,1964110,4627538,11447672,26971268,66721922,157200070,

%U 388883860,916229152,2266581238,5340174842,13210603568,31124819900,76997040170,181408744558,448771637452

%N Numbers n such that 2*n^2 + 41 is a square.

%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0, 6, 0, -1).

%F The bisections modulo 2 satisfy the same recurrence relation a(n+2)=6*a(n+1)-a(n)

%F G.f.: 2*x*(x+1)*(x^2+3*x+1)/(x^2+2*x-1)/(x^2-2*x-1). - _R. J. Mathar_, Nov 14 2007

%t LinearRecurrence[{0, 6, 0, -1}, {2, 8, 20, 50}, 40] (* _T. D. Noe_, Sep 03 2012 *)

%K nonn

%O 1,1

%A _Richard Choulet_, Oct 18 2007

%E a(14)-a(23) from _Donovan Johnson_, Nov 15 2009

%E a(24)-a(30) from _Donovan Johnson_, Sep 01 2012