Number of squarefree palindromes over {0, 1, 2} of length 2n+1.

Terms

a(0) =3a(1) =6a(2) =6a(3) =12a(4) =12a(5) =12a(6) =12a(7) =18a(8) =18a(9) =24a(10) =36a(11) =48a(12) =60a(13) =84a(14) =102a(15) =138a(16) =186a(17) =246a(18) =306a(19) =378a(20) =486a(21) =630a(22) =816a(23) =1050a(24) =1350a(25) =1782a(26) =2328a(27) =2988a(28) =3870a(29) =5076