Number of binary sequences of length n with no initial repeats (or, with no final repeats).

Terms

a(0) =2a(1) =2a(2) =4a(3) =6a(4) =12a(5) =20a(6) =40a(7) =74a(8) =148a(9) =286a(10) =572a(11) =1124a(12) =2248a(13) =4460a(14) =8920a(15) =17768a(16) =35536a(17) =70930a(18) =141860a(19) =283440a(20) =566880a(21) =1133200a(22) =2266400a(23) =4531686a(24) =9063372a(25) =18124522a(26) =36249044a(27) =72493652a(28) =144987304a(29) =289965744