Number of binary strings of length n with no substrings equal to 0000, 0101, or 1111.

Terms

a(0) =1a(1) =2a(2) =4a(3) =8a(4) =13a(5) =22a(6) =37a(7) =62a(8) =104a(9) =174a(10) =292a(11) =490a(12) =821a(13) =1376a(14) =2308a(15) =3870a(16) =6487a(17) =10876a(18) =18237a(19) =30576a(20) =51261a(21) =85946a(22) =144102a(23) =241600a(24) =405064a(25) =679140a(26) =1138659a(27) =1909078a(28) =3200774a(29) =5366466