Number of primitive (period n) periodic palindromes using a maximum of four different symbols.

A056495

Number of primitive (period n) periodic palindromes using a maximum of four different symbols.

Terms

    a(0) =4a(1) =6a(2) =12a(3) =30a(4) =60a(5) =138a(6) =252a(7) =600a(8) =1008a(9) =2490a(10) =4092a(11) =10050a(12) =16380a(13) =40698a(14) =65460a(15) =163200a(16) =262140a(17) =654192a(18) =1048572a(19) =2618850a(20) =4194036a(21) =10481658a(22) =16777212a(23) =41932200a(24) =67108800a(25) =167755770a(26) =268434432a(27) =671047650

External references