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

Terms

a(0) =1a(1) =9a(2) =11a(3) =17a(4) =27a(5) =89a(6) =91a(7) =911a(8) =989a(9) =2777a(10) =2827a(11) =2877a(12) =9911a(13) =27877a(14) =28127a(15) =88189a(16) =88277a(17) =88877a(18) =98989a(19) =99891a(20) =172891a(21) =279127a(22) =282827a(23) =287891a(24) =988877a(25) =2879189a(26) =9989891a(27) =9998891a(28) =29711811a(29) =87919777