Largest palindromic substring in 5^n.

Terms

a(0) =1a(1) =5a(2) =5a(3) =5a(4) =6a(5) =5a(6) =6a(7) =8a(8) =9a(9) =9a(10) =656a(11) =828a(12) =414a(13) =22a(14) =515a(15) =757a(16) =878a(17) =939a(18) =26562a(19) =9a(20) =9a(21) =8a(22) =101a(23) =55a(24) =464a(25) =3223a(26) =11611a(27) =969a(28) =252a(29) =626