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 | 2 |
| 2 | 2 |
| 3 | 222 |
| 4 | -1 |
| 5 | -1 |
| 6 | 222 |
| 7 | 222222 |
| 8 | -1 |
| 9 | 222222222 |
| 10 | -1 |
| 11 | 22 |
| 12 | -1 |
| 13 | 222222 |
| 14 | 222222 |
| 15 | -1 |
| 16 | -1 |
| 17 | 2222222222222222 |
| 18 | 222222222 |
| 19 | 222222222222222222 |
| 20 | -1 |
| 21 | 222222 |
| 22 | 22 |
| 23 | 2222222222222222222222 |
| 24 | -1 |
| 25 | -1 |
| 26 | 222222 |
| 27 | 222222222222222222222222222 |
| 28 | -1 |
| 29 | 2222222222222222222222222222 |
| 30 | -1 |
| 31 | 222222222222222 |
| 32 | -1 |
| 33 | 222222 |
| 34 | 2222222222222222 |
| 35 | -1 |
| 36 | -1 |
| 37 | 222 |
| 38 | 222222222222222222 |
| 39 | 222222 |
| 40 | -1 |
| 41 | 22222 |
| 42 | 222222 |