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) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 8 |
| 4 | 54 |
| 5 | 144 |
| 6 | 2880 |
| 7 | 5760 |
| 8 | 206640 |
| 9 | 1491840 |
| 10 | 24675840 |
| 11 | 43545600 |
| 12 | 10298534400 |
| 13 | 6706022400 |
| 14 | 1195587993600 |
| 15 | 33476463820800 |
| 16 | 775450900224000 |
| 17 | 376610217984000 |
| 18 | 553805325545472000 |
| 19 | 128047474114560000 |
| 20 | 339876410542276608000 |
| 21 | 6208765924866785280000 |