Number of perfect powers (A001597) not exceeding 10^n.

Terms

a(0) =1a(1) =4a(2) =13a(3) =41a(4) =125a(5) =367a(6) =1111a(7) =3395a(8) =10491a(9) =32670a(10) =102231a(11) =320990a(12) =1010196a(13) =3184138a(14) =10046921a(15) =31723592a(16) =100216745a(17) =316694005a(18) =1001003332a(19) =3164437425a(20) =10004650118a(21) =31632790244a(22) =100021566157a(23) =316274216762