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 | 0 |
| 2 | 2 |
| 3 | 0 |
| 4 | 48 |
| 5 | 120 |
| 6 | 4560 |
| 7 | 35700 |
| 8 | 1048992 |
| 9 | 15514128 |
| 10 | 456726240 |
| 11 | 10073339100 |
| 12 | 323266492560 |
| 13 | 9361060088952 |
| 14 | 336767513038320 |
| 15 | 11913610172869860 |
| 16 | 482920107426039360 |
| 17 | 19998225191360977440 |
| 18 | 909512248720724321472 |