Numbers k such that k and k^2 use only the digits 1, 6, 7, 8 and 9.

Terms

a(0) =1a(1) =9a(2) =786a(3) =881a(4) =887a(5) =7867a(6) =8167a(7) =8887a(8) =81619a(9) =81791a(10) =81969a(11) =88776a(12) =88869a(13) =88987a(14) =781791a(15) =819687a(16) =876167a(17) =988776a(18) =988869a(19) =7866187a(20) =7866881a(21) =8168119a(22) =8179119a(23) =8768619a(24) =8819687a(25) =8881886a(26) =78177867a(27) =81718796a(28) =81968176a(29) =87817891