Generalized Pellian with second term of 6.

Terms

a(0) =1a(1) =6a(2) =25a(3) =106a(4) =449a(5) =1902a(6) =8057a(7) =34130a(8) =144577a(9) =612438a(10) =2594329a(11) =10989754a(12) =46553345a(13) =197203134a(14) =835365881a(15) =3538666658a(16) =14990032513a(17) =63498796710a(18) =268985219353