Sequence associated with palindromic structures.

Terms

a(0) =1a(1) =3a(2) =10a(3) =37a(4) =150a(5) =653a(6) =2990a(7) =14157a(8) =68470a(9) =335533a(10) =1657470a(11) =8227277a(12) =40957190a(13) =204250413a(14) =1019649550a(15) =5093448397a(16) =25452860310a(17) =127221189293a(18) =635976675230