Numbers k such that k and k^2 use only the digits 0, 2, 4, 6 and 7.

Terms

a(0) =0a(1) =2a(2) =20a(3) =26a(4) =200a(5) =260a(6) =474a(7) =2000a(8) =2600a(9) =2602a(10) =4740a(11) =4762a(12) =20000a(13) =20602a(14) =26000a(15) =26020a(16) =26602a(17) =47400a(18) =47620a(19) =77474a(20) =77602a(21) =200000a(22) =206020a(23) =260000a(24) =260200a(25) =266020a(26) =474000a(27) =476200a(28) =476474a(29) =476662