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 | 0 |
| 2 | -1 |
| 3 | 3 |
| 4 | -5 |
| 5 | -10 |
| 6 | 146 |
| 7 | -756 |
| 8 | 1086 |
| 9 | 23400 |
| 10 | -300066 |
| 11 | 1855590 |
| 12 | 341826 |
| 13 | -165915828 |
| 14 | 2158958556 |
| 15 | -10006622640 |
| 16 | -172337345496 |
| 17 | 4941605486016 |
| 18 | -64365944851512 |
| 19 | 339328464492456 |
| 20 | 5510899593823176 |
| 21 | -157099566384759600 |
| 22 | 1059259019507498160 |
| 23 | 41957473280879898720 |