Number of binary strings of length n with no substrings equal to 0000, 0011 or 1101.

Terms

a(0) =1a(1) =2a(2) =4a(3) =8a(4) =13a(5) =21a(6) =34a(7) =54a(8) =86a(9) =139a(10) =225a(11) =364a(12) =590a(13) =956a(14) =1547a(15) =2503a(16) =4050a(17) =6552a(18) =10600a(19) =17151a(20) =27751a(21) =44902a(22) =72654a(23) =117558a(24) =190213a(25) =307771a(26) =497984a(27) =805754a(28) =1303736a(29) =2109489