Numbers k such that k and k^2 use only the digits 2, 4, 5, 6 and 7.

Terms

a(0) =2a(1) =5a(2) =24a(3) =25a(4) =26a(5) =65a(6) =74a(7) =75a(8) =76a(9) =275a(10) =474a(11) =475a(12) =476a(13) =524a(14) =525a(15) =526a(16) =665a(17) =674a(18) =675a(19) =725a(20) =2574a(21) =2725a(22) =2765a(23) =4762a(24) =6524a(25) =6525a(26) =6665a(27) =6674a(28) =6675a(29) =6725