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 | 1 |
| 2 | 6 |
| 3 | 42 |
| 4 | 360 |
| 5 | 3720 |
| 6 | 45360 |
| 7 | 640080 |
| 8 | 10281600 |
| 9 | 185431680 |
| 10 | 3712262400 |
| 11 | 81709689600 |
| 12 | 1961511552000 |
| 13 | 51005527372800 |
| 14 | 1428241944729600 |
| 15 | 42848566016256000 |
| 16 | 1371175035310080000 |
| 17 | 46620306887970816000 |
| 18 | 1678337450340655104000 |
| 19 | 63776944758045302784000 |