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 | 13 |
| 2 | 23 |
| 3 | -1 |
| 4 | 43 |
| 5 | 53 |
| 6 | -1 |
| 7 | 73 |
| 8 | 83 |
| 9 | -1 |
| 10 | 103 |
| 11 | 113 |
| 12 | -1 |
| 13 | 1333333333333333 |
| 14 | 1433 |
| 15 | -1 |
| 16 | 163 |
| 17 | 173 |
| 18 | -1 |
| 19 | 193 |
| 20 | 20333 |
| 21 | -1 |
| 22 | 223 |
| 23 | 233 |
| 24 | -1 |
| 25 | 2533333333 |
| 26 | 263 |
| 27 | -1 |
| 28 | 283 |
| 29 | 293 |
| 30 | -1 |
| 31 | 313 |
| 32 | 323333 |
| 33 | -1 |
| 34 | 3433 |
| 35 | 353 |
| 36 | -1 |
| 37 | 373 |
| 38 | 383 |
| 39 | -1 |