Least number x such that x^n has n digits equal to k. Case k=4.

Terms

a(0) =4a(1) =12a(2) =114a(3) =261a(4) =384a(5) =258a(6) =896a(7) =1491a(8) =1739a(9) =2768a(10) =3241a(11) =3974a(12) =1114a(13) =4522a(14) =9368a(15) =5144a(16) =1935a(17) =11982a(18) =8461a(19) =19038a(20) =13692a(21) =25173a(22) =16484a(23) =37477a(24) =21003a(25) =26216a(26) =46587a(27) =42619a(28) =29054a(29) =74082