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 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 6 |
| 5 | 15 |
| 6 | -15 |
| 7 | -210 |
| 8 | 28 |
| 9 | 5292 |
| 10 | 4140 |
| 11 | -208560 |
| 12 | -369864 |
| 13 | 11847264 |
| 14 | 33630688 |
| 15 | -917280000 |
| 16 | -3642944640 |
| 17 | 92903375616 |
| 18 | 479824306944 |
| 19 | -11926470604800 |
| 20 | -76477342307840 |
| 21 | 1892813347934208 |
| 22 | 14591875555074048 |
| 23 | -363945109924577280 |
| 24 | -3293838565260693504 |
| 25 | 83374884181664563200 |