Numbers k such that k and k^2 use only the digits 1, 2, 4 and 7.
A136996
Numbers k such that k and k^2 use only the digits 1, 2, 4 and 7.
Terms
- a(0) =1a(1) =2a(2) =11a(3) =12a(4) =21a(5) =421a(6) =1214171a(7) =2777177421
External references
- oeis: A136996