Number of periodic palindromic structures using a maximum of five different symbols.

Terms

a(0) =1a(1) =1a(2) =2a(3) =2a(4) =5a(5) =5a(6) =13a(7) =15a(8) =41a(9) =52a(10) =143a(11) =202a(12) =564a(13) =855a(14) =2433a(15) =3845a(16) =11101a(17) =18002a(18) =52662a(19) =86472a(20) =255128a(21) =422005a(22) =1252898a(23) =2079475a(24) =6197590a(25) =10306752a(26) =30796243a(27) =51263942a(28) =153411664a(29) =255514355