Numbers k such that k and k^2 use only the digits 4, 5, 7, 8 and 9.

Terms

a(0) =7a(1) =88a(2) =888a(3) =7588a(4) =9878a(5) =75888a(6) =885888a(7) =989878a(8) =7479878a(9) =7589457a(10) =7745957a(11) =9775457a(12) =97748957a(13) =744888978a(14) =757944588a(15) =945985457a(16) =7475598878a(17) =9948757588a(18) =88757455957a(19) =99977995478a(20) =747595978788a(21) =947878988978a(22) =948445875888a(23) =994477479878a(24) =997494589457