Numbers k such that k and k^2 use only the digits 1, 3, 6, 7 and 8.

Terms

a(0) =1a(1) =6a(2) =131a(3) =876a(4) =881a(5) =8131a(6) =8876a(7) =11731a(8) =13181a(9) =18376a(10) =18381a(11) =37131a(12) =88776a(13) =116881a(14) =117181a(15) =117776a(16) =133181a(17) =183776a(18) =336731a(19) =888131a(20) =1366881a(21) =1373376a(22) =3336731a(23) =3371376a(24) =3713181a(25) =6113376a(26) =7866881a(27) =11761731a(28) =13167131a(29) =13717776