Number of binary strings of length n having at least one run of length at least 4.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =2a(5) =6a(6) =16a(7) =40a(8) =94a(9) =214a(10) =476a(11) =1040a(12) =2242a(13) =4782a(14) =10112a(15) =21232a(16) =44318a(17) =92046a(18) =190364a(19) =392264a(20) =805746a(21) =1650518a(22) =3372816a(23) =6877656a(24) =13998142a(25) =28442918a(26) =57707324a(27) =116925600a(28) =236630274a(29) =478372062