Number of (3+)-free binary strings of length n.

Terms

a(0) =1a(1) =2a(2) =4a(3) =8a(4) =14a(5) =26a(6) =48a(7) =86a(8) =156a(9) =282a(10) =506a(11) =910a(12) =1638a(13) =2936a(14) =5276a(15) =9482a(16) =17012a(17) =30542a(18) =54838a(19) =98440a(20) =176726a(21) =317268a(22) =569516a(23) =1022368a(24) =1835320a(25) =3294596a(26) =5914262a(27) =10616932a(28) =19058674a(29) =34212776