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 | -1 |
| 2 | 60 |
| 3 | -162 |
| 4 | -5280 |
| 5 | 20250 |
| 6 | 128520 |
| 7 | -569380 |
| 8 | -1854720 |
| 9 | 9338490 |
| 10 | 20097000 |
| 11 | -113704668 |
| 12 | -181621440 |
| 13 | 1142905764 |
| 14 | 1447926480 |
| 15 | -10042461000 |
| 16 | -10529925120 |
| 17 | 79859881530 |
| 18 | 71384175720 |
| 19 | -587933314540 |
| 20 | -457825368000 |
| 21 | 4070529226764 |