Numbers k such that k and k^2 use only the digits 0, 2, 7, 8 and 9.

Terms

a(0) =0a(1) =27a(2) =270a(3) =297a(4) =2700a(5) =2970a(6) =2997a(7) =27000a(8) =28297a(9) =29700a(10) =29970a(11) =29997a(12) =88277a(13) =270000a(14) =282970a(15) =297000a(16) =298027a(17) =299700a(18) =299970a(19) =299997a(20) =882770a(21) =2700000a(22) =2787997a(23) =2829700a(24) =2970000a(25) =2980270a(26) =2997000a(27) =2999700a(28) =2999970a(29) =2999997