Numbers k such that k and k^2 use only the digits 1, 2, 5, 6 and 7.

Terms

a(0) =1a(1) =5a(2) =11a(3) =15a(4) =16a(5) =25a(6) =26a(7) =75a(8) =76a(9) =125a(10) =165a(11) =166a(12) =275a(13) =276a(14) =511a(15) =515a(16) =516a(17) =525a(18) =526a(19) =715a(20) =716a(21) =725a(22) =1125a(23) =1275a(24) =1665a(25) =1666a(26) =2261a(27) =2275a(28) =2675a(29) =5125