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) |
|---|---|
| 2 | 1 |
| 3 | 5 |
| 4 | 22 |
| 5 | 114 |
| 6 | 696 |
| 7 | 4920 |
| 8 | 39600 |
| 9 | 357840 |
| 10 | 3588480 |
| 11 | 39553920 |
| 12 | 475372800 |
| 13 | 6187104000 |
| 14 | 86699289600 |
| 15 | 1301447347200 |
| 16 | 20835611596800 |
| 17 | 354379753728000 |
| 18 | 6381450915840000 |
| 19 | 121289412980736000 |
| 20 | 2426499634470912000 |