Numbers k such that k and k^2 use only the digits 0, 4, 7 and 8.

Terms

a(0) =0a(1) =88a(2) =878a(3) =880a(4) =8780a(5) =8800a(6) =87800a(7) =88000a(8) =878000a(9) =880000a(10) =8780000a(11) =8800000a(12) =87800000a(13) =88000000a(14) =878000000a(15) =880000000a(16) =8780000000a(17) =8800000000a(18) =87800000000a(19) =88000000000a(20) =878000000000a(21) =880000000000