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

Terms

a(0) =1a(1) =11a(2) =26a(3) =261a(4) =276a(5) =826a(6) =881a(7) =1126a(8) =1276a(9) =2681a(10) =8881a(11) =78181a(12) =78881a(13) =82261a(14) =88776a(15) =161761a(16) =261126a(17) =277826a(18) =1128126a(19) =1271881a(20) =1618276a(21) =7866881a(22) =8226276a(23) =8287811a(24) =8878126a(25) =11281276a(26) =12722681a(27) =26781761a(28) =27717826a(29) =78221881