Largest palindromic substring in 7^n.

Terms

a(0) =1a(1) =7a(2) =9a(3) =343a(4) =4a(5) =8a(6) =11a(7) =8a(8) =8a(9) =353a(10) =282a(11) =77a(12) =8a(13) =88a(14) =22a(15) =747a(16) =696a(17) =232a(18) =979a(19) =9889a(20) =2662a(21) =85458a(22) =909a(23) =747a(24) =414a(25) =686a(26) =77a(27) =363a(28) =99a(29) =797