Number of SiC polytypes that repeat after 2n layers.

Terms

a(0) =0a(1) =0a(2) =1a(3) =1a(4) =0a(5) =1a(6) =1a(7) =1a(8) =1a(9) =3a(10) =3a(11) =4a(12) =7a(13) =11a(14) =15a(15) =24a(16) =36a(17) =55a(18) =81a(19) =129a(20) =195a(21) =301a(22) =465a(23) =728a(24) =1116a(25) =1745a(26) =2717a(27) =4239a(28) =6603a(29) =10357