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 | -9 |
| 2 | 72 |
| 3 | -585 |
| 4 | 4734 |
| 5 | -38358 |
| 6 | 310662 |
| 7 | -2516481 |
| 8 | 20383110 |
| 9 | -165104478 |
| 10 | 1337341896 |
| 11 | -10832484474 |
| 12 | 87743071332 |
| 13 | -710719065000 |
| 14 | 5756823757890 |
| 15 | -46630274845905 |
| 16 | 377705217526470 |
| 17 | -3059412293786310 |
| 18 | 24781239462988800 |
| 19 | -200728040080084110 |
| 20 | 1625897123058144420 |