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 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 0 |
| 7 | 720 |
| 8 | 46080 |
| 9 | 2073600 |
| 10 | 83635200 |
| 11 | 3284582400 |
| 12 | 130292997120 |
| 13 | 5315938467840 |
| 14 | 225174409574400 |
| 15 | 9949921392153600 |
| 16 | 459690572096870400 |
| 17 | 22223242784959856640 |
| 18 | 1124142765926532618240 |
| 19 | 59464928954695680000000 |
| 20 | 3286601083552719895603200 |