Number of periodic palindromic structures of length n using an infinite alphabet.

Terms

a(0) =1a(1) =1a(2) =2a(3) =2a(4) =5a(5) =5a(6) =13a(7) =15a(8) =41a(9) =52a(10) =144a(11) =203a(12) =578a(13) =877a(14) =2605a(15) =4140a(16) =12869a(17) =21147a(18) =69178a(19) =115975a(20) =398766a(21) =678570a(22) =2450406a(23) =4213597a(24) =15939952a(25) =27644437a(26) =109304914a(27) =190899322a(28) =787016238a(29) =1382958545