a(1) = 1 and then smallest nontrivial n-th power starting with 1.

Terms

a(0) =1a(1) =16a(2) =125a(3) =16a(4) =1024a(5) =15625a(6) =128a(7) =1679616a(8) =19683a(9) =1024a(10) =177147a(11) =16777216a(12) =1594323a(13) =16384a(14) =14348907a(15) =152587890625a(16) =131072a(18) =1162261467a(19) =1048576a(20) =10460353203a(23) =16777216