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 | -120 |
| 2 | 20520 |
| 3 | -3934560 |
| 4 | 793510440 |
| 5 | -164694615120 |
| 6 | 34824089129760 |
| 7 | -7460017581785280 |
| 8 | 1613575314347164200 |
| 9 | -351613291994820018840 |
| 10 | 77073167391611232305520 |
| 11 | -16975579813113940564868640 |
| 12 | 3753822590560913900129106720 |