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 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 120 |
| 6 | -360 |
| 7 | 1680 |
| 8 | -10080 |
| 9 | 72576 |
| 10 | 1209600 |
| 11 | -14256000 |
| 12 | 159667200 |
| 13 | -1902700800 |
| 14 | 24458353920 |
| 15 | -120860812800 |
| 16 | -193037644800 |
| 17 | 23690780467200 |
| 18 | -646842994237440 |
| 19 | 14916006359654400 |
| 20 | -230812655044608000 |
| 21 | 3182953434006528000 |
| 22 | -37667817509059584000 |