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 | 2 |
| 3 | 6 |
| 4 | 32 |
| 5 | 200 |
| 6 | 1536 |
| 7 | 13664 |
| 8 | 139264 |
| 9 | 1595520 |
| 10 | 20316160 |
| 11 | 284534272 |
| 12 | 4347396096 |
| 13 | 71958415360 |
| 14 | 1282685272064 |
| 15 | 24497477345280 |
| 16 | 499058556796928 |
| 17 | 10802158189445120 |
| 18 | 247567232110952448 |
| 19 | 5989035387568652288 |