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 | 6 |
| 5 | 24 |
| 6 | 120 |
| 7 | 640 |
| 8 | 3150 |
| 9 | 16128 |
| 10 | 94080 |
| 11 | 614400 |
| 12 | 3801600 |
| 13 | 26864640 |
| 14 | 203174400 |
| 15 | 1757184000 |
| 16 | 11783772000 |
| 17 | 95122227200 |
| 18 | 794598604800 |
| 19 | 7821066240000 |
| 20 | 65767223808000 |
| 21 | 675845406720000 |
| 22 | 6895980748800000 |
| 23 | 83909612666880000 |
| 24 | 784784318782464000 |