The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 3 |
| 3 | 5 |
| 4 | 7 |
| 5 | 41 |
| 6 | 47 |
| 7 | 14741 |
| 8 | 14747 |
| 9 | 74747 |
| 10 | 1414741 |
| 11 | 1474141 |
| 12 | 7414741 |
| 13 | 4141414747 |
| 14 | 4147414147 |
| 15 | 14141414141 |
| 16 | 14141414741 |
| 17 | 14141474741 |
| 18 | 14141474747 |
| 19 | 14147414741 |
| 20 | 14147474141 |
| 21 | 14147474147 |
| 22 | 14741414747 |
| 23 | 74141414147 |
| 24 | 74141414741 |
| 25 | 74147414741 |
| 26 | 74741474741 |
| 27 | 74747414141 |
[2,3,5,7,41,47,14741,14747,74747,1414741,1474141, 7414741,4141414747,4147414147,14141414141, 14141414741,14141474741,14141474747,14147414741, 14147474141,14147474147,14741414747,74141414147, 74141414741,74147414741,74741474741,74747414141] |