Generalized Pellian with second term of 9.

Terms

a(0) =1a(1) =9a(2) =37a(3) =157a(4) =665a(5) =2817a(6) =11933a(7) =50549a(8) =214129a(9) =907065a(10) =3842389a(11) =16276621a(12) =68948873a(13) =292072113a(14) =1237237325a(15) =5241021413a(16) =22201322977a(17) =94046313321a(18) =398386576261