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 | 0 |
| 2 | 2 |
| 3 | 4 |
| 4 | 3 |
| 5 | 7 |
| 6 | 8 |
| 7 | -1 |
| 8 | 9 |
| 9 | 10 |
| 10 | 12 |
| 11 | 16 |
| 12 | -1 |
| 13 | 11 |
| 14 | 18 |
| 15 | 15 |
| 16 | 24 |
| 17 | 20 |
| 18 | 25 |
| 19 | 22 |
| 20 | 21 |
| 21 | -1 |
| 22 | 23 |