Number of binary strings of length n with no substrings equal to 0000, 0001 or 1001.

Terms

a(0) =1a(1) =2a(2) =4a(3) =8a(4) =13a(5) =22a(6) =36a(7) =58a(8) =94a(9) =152a(10) =246a(11) =398a(12) =644a(13) =1042a(14) =1686a(15) =2728a(16) =4414a(17) =7142a(18) =11556a(19) =18698a(20) =30254a(21) =48952a(22) =79206a(23) =128158a(24) =207364a(25) =335522a(26) =542886a(27) =878408a(28) =1421294a(29) =2299702