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 | 1 |
| 2 | 1 |
| 3 | -2 |
| 4 | -9 |
| 5 | 4 |
| 6 | 75 |
| 7 | 24 |
| 8 | -735 |
| 9 | -816 |
| 10 | 8505 |
| 11 | 17760 |
| 12 | -114345 |
| 13 | -388800 |
| 14 | 1756755 |
| 15 | 9233280 |
| 16 | -30405375 |
| 17 | -242968320 |
| 18 | 585810225 |
| 19 | 7125511680 |
| 20 | -12439852425 |
| 21 | -232838323200 |
| 22 | 288735522075 |
| 23 | 8450546227200 |
| 24 | -7273385294175 |
| 25 | -339004760371200 |
| 26 | 197646339515625 |
| 27 | 14945696794828800 |
| 28 | -5763367260275625 |