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

Terms

a(0) =0a(1) =0a(2) =1a(3) =2a(4) =3a(5) =5a(6) =9a(7) =17a(8) =31a(9) =60a(10) =113a(11) =220a(12) =419a(13) =813a(14) =1565a(15) =3033a(16) =5855a(17) =11358a(18) =21977a(19) =42644a(20) =82675a(21) =160517a(22) =311609a(23) =605551a(24) =1176871a(25) =2288964a(26) =4453237a(27) =8669002a(28) =16881859a(29) =32892459