Number of primitive (aperiodic) palindromes using exactly five different symbols.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =0a(8) =120a(9) =120a(10) =1800a(11) =1800a(12) =16800a(13) =16800a(14) =126000a(15) =126000a(16) =834120a(17) =834000a(18) =5103000a(19) =5102880a(20) =29607600a(21) =29605800a(22) =165528000a(23) =165526200a(24) =901020120a(25) =901003320a(26) =4809004080a(27) =4808987400a(28) =25292030400a(29) =25291904280