Number of binary necklaces with n beads and at least four consecutive black beads.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =2a(5) =3a(6) =5a(7) =9a(8) =17a(9) =33a(10) =63a(11) =124a(12) =241a(13) =475a(14) =930a(15) =1831a(16) =3593a(17) =7077a(18) =13905a(19) =27377a(20) =53847a(21) =106006a(22) =208601a(23) =410723a(24) =808514a(25) =1592123a(26) =3135085a(27) =6174695a(28) =12161761a(29) =23957945