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 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 16 |
| 6 | 60 |
| 7 | 240 |
| 8 | 840 |
| 9 | 3584 |
| 10 | 16800 |
| 11 | 96000 |
| 12 | 475200 |
| 13 | 3041280 |
| 14 | 19219200 |
| 15 | 153753600 |
| 16 | 864864000 |
| 17 | 6560153600 |
| 18 | 47048601600 |
| 19 | 439934976000 |
| 20 | 3192583680000 |
| 21 | 31434670080000 |
| 22 | 280947363840000 |
| 23 | 3296449069056000 |
| 24 | 27139515346944000 |
| 25 | 308787374614118400 |