Number of ternary palindromes of length 2n+1 having no (7/4)+ powers.

Terms

a(0) =3a(1) =6a(2) =6a(3) =12a(4) =12a(5) =6a(6) =6a(7) =6a(8) =6a(9) =6a(10) =12a(11) =12a(12) =18a(13) =30a(14) =30a(15) =36a(16) =54a(17) =66a(18) =72a(19) =90a(20) =96a(21) =114a(22) =168a(23) =210a(24) =252a(25) =330a(26) =414a(27) =486a(28) =618a(29) =756