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 | 0 |
| 3 | -6 |
| 4 | -12 |
| 5 | 20 |
| 6 | 300 |
| 7 | 252 |
| 8 | -3024 |
| 9 | -36720 |
| 10 | 106560 |
| 11 | 110880 |
| 12 | 12212640 |
| 13 | -125629920 |
| 14 | 1005286464 |
| 15 | -16865735040 |
| 16 | 252900345600 |
| 17 | -3575747185920 |
| 18 | 58447092395520 |
| 19 | -1014901444454400 |
| 20 | 18218754479923200 |
| 21 | -346655486035998720 |
| 22 | 6952232946445839360 |
| 23 | -145913061049673702400 |
| 24 | 3205301440394904238080 |