Numbers k such that k and k^2 use only the digits 1, 5, 6, 7 and 8.

Terms

a(0) =1a(1) =76a(2) =81a(3) =766a(4) =816a(5) =881a(6) =7181a(7) =7666a(8) =71881a(9) =76666a(10) =81681a(11) =81766a(12) =88181a(13) =88776a(14) =766666a(15) =767181a(16) =817666a(17) =817776a(18) =876766a(19) =7666666a(20) =7866881a(21) =8115766a(22) =8176666a(23) =76666666a(24) =81766666a(25) =81767181a(26) =87617166a(27) =87857166a(28) =88157181a(29) =88761881