Pisot sequence L(2,7).

Terms

a(0) =2a(1) =7a(2) =25a(3) =90a(4) =324a(5) =1167a(6) =4204a(7) =15145a(8) =54561a(9) =196561a(10) =708130a(11) =2551107a(12) =9190611a(13) =33110070a(14) =119282248a(15) =429725902a(16) =1548129365a(17) =5577286637a(18) =20092717660a(19) =72385969961a(20) =260777498389a(21) =939476306012