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

A056515

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

Terms

    a(0) =1a(1) =1a(2) =1a(3) =1a(4) =3a(5) =4a(6) =10a(7) =14a(8) =35a(9) =49a(10) =127a(11) =186a(12) =463a(13) =714a(14) =1799a(15) =2789a(16) =6996a(17) =11050a(18) =27685a(19) =43946a(20) =109925a(21) =175259a(22) =438495a(23) =700074a(24) =1750445a(25) =2798246a(26) =6996927a(27) =11188856a(28) =27973533a(29) =44747434

External references