This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | -1 |
| 3 | 111 |
| 4 | -1 |
| 5 | -1 |
| 6 | -1 |
| 7 | 111111 |
| 8 | -1 |
| 9 | 111111111 |
| 10 | -1 |
| 11 | 11 |
| 12 | -1 |
| 13 | 111111 |
| 14 | -1 |
| 15 | -1 |
| 16 | -1 |
| 17 | 1111111111111111 |
| 18 | -1 |
| 19 | 111111111111111111 |
| 20 | -1 |
| 21 | 111111 |
| 22 | -1 |
| 23 | 1111111111111111111111 |
| 24 | -1 |
| 25 | -1 |
| 26 | -1 |
| 27 | 111111111111111111111111111 |
| 28 | -1 |
| 29 | 1111111111111111111111111111 |
| 30 | -1 |
| 31 | 111111111111111 |
| 32 | -1 |
| 33 | 111111 |
| 34 | -1 |
| 35 | -1 |
| 36 | -1 |
| 37 | 111 |
| 38 | -1 |
| 39 | 111111 |
| 40 | -1 |
| 41 | 11111 |
| 42 | -1 |