Numbers k such that k and k^2 use only the digits 2, 5, 6, 7 and 8.

Terms

a(0) =5a(1) =25a(2) =26a(3) =75a(4) =76a(5) =85a(6) =275a(7) =525a(8) =526a(9) =725a(10) =765a(11) =766a(12) =826a(13) =875a(14) =2585a(15) =2785a(16) =2875a(17) =5275a(18) =7525a(19) =7665a(20) =7666a(21) =8525a(22) =8675a(23) =8765a(24) =8865a(25) =8875a(26) =26875a(27) =27525a(28) =27725a(29) =28675