Least roots of perfect powers (A001597).

Terms

a(0) =1a(1) =2a(2) =2a(3) =3a(4) =2a(5) =5a(6) =3a(7) =2a(8) =6a(9) =7a(10) =2a(11) =3a(12) =10a(13) =11a(14) =5a(15) =2a(16) =12a(17) =13a(18) =14a(19) =6a(20) =15a(21) =3a(22) =2a(23) =17a(24) =18a(25) =7a(26) =19a(27) =20a(28) =21a(29) =22