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 | 9 |
| 2 | 75 |
| 3 | 660 |
| 4 | 6300 |
| 5 | 65520 |
| 6 | 740880 |
| 7 | 9072000 |
| 8 | 119750400 |
| 9 | 1696464000 |
| 10 | 25686460800 |
| 11 | 414096883200 |
| 12 | 7083236160000 |
| 13 | 128152088064000 |
| 14 | 2445351068160000 |
| 15 | 49084865077248000 |
| 16 | 1033983353475072000 |
| 17 | 22808456326656000000 |
| 18 | 525810946517176320000 |
| 19 | 12645008187498086400000 |