Number of binary strings of length n that begin with an odd-length palindrome.

Terms

a(0) =0a(1) =0a(2) =0a(3) =4a(4) =8a(5) =20a(6) =40a(7) =88a(8) =176a(9) =364a(10) =728a(11) =1480a(12) =2960a(13) =5960a(14) =11920a(15) =23920a(16) =47840a(17) =95828a(18) =191656a(19) =383608a(20) =767216a(21) =1535000a(22) =3070000a(23) =6141136a(24) =12282272a(25) =24566776a(26) =49133552a(27) =98271568a(28) =196543136a(29) =393095120