Even palindromes.

Terms

a(0) =0a(1) =2a(2) =4a(3) =6a(4) =8a(5) =22a(6) =44a(7) =66a(8) =88a(9) =202a(10) =212a(11) =222a(12) =232a(13) =242a(14) =252a(15) =262a(16) =272a(17) =282a(18) =292a(19) =404a(20) =414a(21) =424a(22) =434a(23) =444a(24) =454a(25) =464a(26) =474a(27) =484a(28) =494a(29) =606