Numbers k such that k and k^2 use only the digits 1, 2, 4, 6 and 7.

Terms

a(0) =1a(1) =2a(2) =4a(3) =11a(4) =12a(5) =21a(6) =26a(7) =42a(8) =46a(9) =121a(10) =162a(11) =276a(12) =421a(13) =474a(14) =642a(15) =1474a(16) =1621a(17) =1662a(18) =2162a(19) =2174a(20) =4174a(21) =4761a(22) =4762a(23) =4771a(24) =6424a(25) =6642a(26) =11142a(27) =16662a(28) =21621a(29) =24724