Number of binary strings of length n whose only palindromic prefixes are "1" and "11".

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =5a(5) =8a(6) =15a(7) =27a(8) =52a(9) =99a(10) =195a(11) =382a(12) =757a(13) =1499a(14) =2986a(15) =5945a(16) =11865a(17) =23678a(18) =47309a(19) =94519a(20) =188942a(21) =377689a(22) =755191a(23) =1510000a(24) =3019625a(25) =6038493a(26) =12076244a(27) =24150989a(28) =48300491a(29) =96597996