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) |
|---|---|
| 2 | 0 |
| 3 | 9 |
| 4 | 84 |
| 5 | 720 |
| 6 | 6480 |
| 7 | 63000 |
| 8 | 665280 |
| 9 | 7620480 |
| 10 | 94348800 |
| 11 | 1257379200 |
| 12 | 17962560000 |
| 13 | 273988915200 |
| 14 | 4446092851200 |
| 15 | 76498950528000 |
| 16 | 1391365527552000 |
| 17 | 26676557107200000 |
| 18 | 537799391281152000 |
| 19 | 11373816888225792000 |
| 20 | 251805357846282240000 |
| 21 | 5824367407574876160000 |