Numbers k such that k and k^2 use only the digits 1, 3, 7, 8 and 9.

Terms

a(0) =1a(1) =3a(2) =9a(3) =891a(4) =9891a(5) =13391a(6) =131833a(7) =197917a(8) =993891a(9) =1173833a(10) =1178891a(11) =1331833a(12) =1837917a(13) =1931833a(14) =13318333a(15) =13331833a(16) =19318333a(17) =117787917a(18) =133318333a(19) =193318333a(20) =199971833a(21) =879733891a(22) =1333183333a(23) =1333318333a(24) =1837878891a(25) =1933183333a(26) =1998333891a(27) =3737883333a(28) =8819398391a(29) =8879178891