a(n) is the smallest n-digit cube.

Terms

a(0) =1a(1) =27a(2) =125a(3) =1000a(4) =10648a(5) =103823a(6) =1000000a(7) =10077696a(8) =100544625a(9) =1000000000a(10) =10007873875a(11) =100026577288a(12) =1000000000000