Numbers k such that k and k^2 use only the digits 1, 2, 3, 7 and 8.

Terms

a(0) =1a(1) =11a(2) =111a(3) =1311a(4) =13311a(5) =17811a(6) =133311a(7) =288311a(8) =883811a(9) =1333311a(10) =1823111a(11) =3373111a(12) =13333311a(13) =87828311a(14) =88781311a(15) =133333311a(16) =178387811a(17) =878133311a(18) =888137811a(19) =1333333311a(20) =1372178311a(21) =3337231311a(22) =8881287811a(23) =13183783111a(24) =13333333311a(25) =17712178811a(26) =27781781311a(27) =117183137811a(28) =133333333311a(29) =137373112811