Smallest powerful number such that a(n)-n is also powerful.

Terms

a(0) =9a(1) =27a(2) =4a(3) =8a(4) =9a(5) =214375a(6) =8a(7) =9a(8) =25a(9) =2197a(10) =27a(11) =16a(12) =49a(13) =30459375a(14) =16a(15) =25a(16) =25a(17) =27a(18) =27a(19) =36a(20) =25a(21) =49a(22) =27a(23) =25a(24) =125a(25) =27a(26) =36a(27) =32a(28) =225a(29) =6889