Number of primitive (aperiodic) palindromes using a maximum of three different symbols.

Terms

a(0) =3a(1) =0a(2) =6a(3) =6a(4) =24a(5) =18a(6) =78a(7) =72a(8) =234a(9) =216a(10) =726a(11) =696a(12) =2184a(13) =2106a(14) =6528a(15) =6480a(16) =19680a(17) =19422a(18) =59046a(19) =58800a(20) =177060a(21) =176418a(22) =531438a(23) =530640a(24) =1594296a(25) =1592136a(26) =4782726a(27) =4780776a(28) =14348904a(29) =14342112