Number of n-digit perfect powers.

Terms

a(0) =4a(1) =8a(2) =28a(3) =84a(4) =242a(5) =744a(6) =2284a(7) =7096a(8) =22179a(9) =69561a(10) =218759a(11) =689206a(12) =2173942a(13) =6862783a(14) =21676671a(15) =68493153a(16) =216477260a(17) =684309327a(18) =2163434093a(19) =6840212693a(20) =21628140126a(21) =68388775913a(22) =216252650605a(23) =683825838922