Pisot sequences L(3,7) or S(3,7).

Terms

a(0) =3a(1) =7a(2) =17a(3) =42a(4) =104a(5) =258a(6) =641a(7) =1593a(8) =3959a(9) =9840a(10) =24458a(11) =60793a(12) =151108a(13) =375597a(14) =933592a(15) =2320557a(16) =5768028a(17) =14337139a(18) =35636713a(19) =88579410a(20) =220174961a(21) =547271804a(22) =1360311028a(23) =3381219496a(24) =8404434755a(25) =20890250880a(26) =51925274519a(27) =129066622961a(28) =320810882887