Number of ZnS polytypes that repeat after n layers.

Terms

a(0) =0a(1) =1a(2) =1a(3) =1a(4) =1a(5) =2a(6) =3a(7) =6a(8) =10a(9) =18a(10) =31a(11) =59a(12) =105a(13) =198a(14) =365a(15) =688a(16) =1285a(17) =2438a(18) =4599a(19) =8755a(20) =16647a(21) =31806a(22) =60787a(23) =116570a(24) =223696a(25) =430290a(26) =828514a(27) =1598025a(28) =3085465a(29) =5965612