Number of binary words of length n that are not "bifix-free".

Terms

a(0) =0a(1) =0a(2) =2a(3) =4a(4) =10a(5) =20a(6) =44a(7) =88a(8) =182a(9) =364a(10) =740a(11) =1480a(12) =2980a(13) =5960a(14) =11960a(15) =23920a(16) =47914a(17) =95828a(18) =191804a(19) =383608a(20) =767500a(21) =1535000a(22) =3070568a(23) =6141136a(24) =12283388a(25) =24566776a(26) =49135784a(27) =98271568a(28) =196547560a(29) =393095120