Floor(6^n/(1+1/(2*cos(5*Pi/11)))^n).

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =4a(6) =5a(7) =7a(8) =9a(9) =12a(10) =17a(11) =22a(12) =30a(13) =40a(14) =53a(15) =71a(16) =95a(17) =126a(18) =168a(19) =223a(20) =297a(21) =395a(22) =525a(23) =698a(24) =928a(25) =1234a(26) =1640a(27) =2180a(28) =2899a(29) =3854