Numbers k such that k and k^2 use only the digits 4, 6, 7, 8 and 9.

Terms

a(0) =7a(1) =8a(2) =67a(3) =88a(4) =667a(5) =864a(6) =886a(7) =887a(8) =974a(9) =6667a(10) =8874a(11) =8887a(12) =66667a(13) =68474a(14) =86478a(15) =87664a(16) =94788a(17) =94867a(18) =98978a(19) =666667a(20) =947886a(21) =947887a(22) =948678a(23) =984878a(24) =988878a(25) =988887a(26) =6666667a(27) =6846886a(28) =6974788a(29) =6974867