Numbers k such that k and k^2 use only the digits 2, 5, 7, 8 and 9.

Terms

a(0) =5a(1) =27a(2) =77a(3) =85a(4) =527a(5) =727a(6) =7227a(7) =9777a(8) =28277a(9) =29585a(10) =88277a(11) =99277a(12) =278527a(13) =298827a(14) =2788527a(15) =2789227a(16) =5289227a(17) =8875727a(18) =9889277a(19) =22925527a(20) =27797977a(21) =29879585a(22) =52898827a(23) =85298827a(24) =88875527a(25) =99789227a(26) =99988777a(27) =278889277a(28) =287279585a(29) =292898827