Pisot sequence P(2,9).

Terms

a(0) =2a(1) =9a(2) =40a(3) =178a(4) =792a(5) =3524a(6) =15680a(7) =69768a(8) =310432a(9) =1381264a(10) =6145920a(11) =27346208a(12) =121676672a(13) =541399104a(14) =2408949760a(15) =10718597248a(16) =47692288512a(17) =212206348544a(18) =944209971200