Numbers k such that k and k^2 use only the digits 1, 5, 7, 8 and 9.

Terms

a(0) =1a(1) =9a(2) =9859a(3) =99859a(4) =771891a(5) =987917a(6) =8879859a(7) =75879891a(8) =75891891a(9) =89191859a(10) =98575859a(11) =881575859a(12) =985889891a(13) =999575859a(14) =999787917a(15) =7181581859a(16) =8881991891a(17) =8885875859a(18) =8888171859a(19) =8897857917a(20) =71775871859a(21) =88758771891a(22) =88881717917a(23) =99597789891a(24) =99857857917a(25) =99997857917a(26) =99999575859a(27) =718175178891a(28) =871711871891a(29) =888571871891