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) |
|---|---|
| 1 | 1 |
| 2 | -1 |
| 3 | -2 |
| 4 | 48 |
| 5 | 30240 |
| 6 | -1596672000 |
| 7 | -18172937502720000 |
| 8 | 122457316443772566896640000 |
| 9 | 1284319496829094129116119090331648000000 |
| 10 | -55603466527142141932748234118927499493985767915520000000 |