1,2

Recurrence: a(1)=1, a(2)=3, a(3)=14*a(1)+a(2), a(4)=14*a(2)+a(1) then a(n)=14*a(n-2)-a(n-4)

G.f.: x(-3*x^3 - x^2 + 43*x + 17)/(x^4 - 14*x^2 + 1).

a(2n) = 4*A007655(n)-A001570(n-1), a(2n+1) = 4*A007655(n)+A001570(n).

12*1^2+13=5^2

12*3^2+13=11^2

12*17^2+13=59^2

Cf. A106257.

Adjacent sequences: A106253 A106254 A106255 this_sequence A106257 A106258 A106259

Sequence in context: A092347 A126587 A108126 this_sequence A091624 A106078 A087908

nonn

Pierre CAMI (pierrecami(AT)tele2.fr), Apr 28 2005

Edited by Ralf Stephan, Jun 1 2007