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 | 0 |
| 1 | 0 |
| 2 | 2 |
| 3 | 12 |
| 4 | 168 |
| 5 | 3120 |
| 6 | 75600 |
| 7 | 2237760 |
| 8 | 78382080 |
| 9 | 3169393920 |
| 10 | 145297152000 |
| 11 | 7446479040000 |
| 12 | 421880659200000 |
| 13 | 26181558769766400 |
| 14 | 1766275594501017600 |
| 15 | 128700516232544256000 |
| 16 | 10073126652104355840000 |