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) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 9 |
| 3 | 18 |
| 4 | 0 |
| 5 | -162 |
| 6 | -567 |
| 7 | 0 |
| 8 | 8019 |
| 9 | 31590 |
| 10 | 0 |
| 11 | -520506 |
| 12 | -2160756 |
| 13 | 0 |
| 14 | 38480265 |
| 15 | 164549880 |
| 16 | 0 |
| 17 | -3072083274 |
| 18 | -13390246485 |
| 19 | 0 |
| 20 | 258054995016 |
| 21 | 1139882486490 |
| 22 | 0 |
| 23 | -22474826957232 |
| 24 | -100257845970825 |
| 25 | 0 |
| 26 | 2011064804461548 |
| 27 | 9039247392729582 |
| 28 | 0 |
| 29 | -183769714890451800 |