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 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 6 |
| 5 | 12 |
| 6 | 40 |
| 7 | 240 |
| 8 | 480 |
| 9 | 1920 |
| 10 | 6912 |
| 11 | 20736 |
| 12 | 76032 |
| 13 | 253440 |
| 14 | 608256 |
| 15 | 4257792 |
| 16 | 7983360 |
| 17 | 26611200 |
| 18 | 88704000 |
| 19 | 319334400 |
| 20 | 1277337600 |
| 21 | 5109350400 |
| 22 | 19508428800 |
| 23 | 73156608000 |
| 24 | 336520396800 |
| 25 | 1177821388800 |
| 26 | 6281714073600 |
| 27 | 23332080844800 |
| 28 | 66663088128000 |