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 | 1 |
| 2 | 0 |
| 3 | 2 |
| 4 | 8 |
| 5 | 48 |
| 6 | 240 |
| 7 | 1968 |
| 8 | 13824 |
| 9 | 140160 |
| 10 | 1263360 |
| 11 | 15298560 |
| 12 | 168422400 |
| 13 | 2373073920 |
| 14 | 30865121280 |
| 15 | 496199854080 |
| 16 | 7445355724800 |
| 17 | 134510244986880 |
| 18 | 2287168006717440 |
| 19 | 45877376537395200 |
| 20 | 871804170613555200 |
| 21 | 19225435113632563200 |
| 22 | 403779880746418176000 |