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 | 0 |
| 2 | 2 |
| 3 | 0 |
| 4 | 12 |
| 5 | 60 |
| 6 | 120 |
| 7 | 2520 |
| 8 | 15120 |
| 9 | 90720 |
| 10 | 1693440 |
| 11 | 13305600 |
| 12 | 140374080 |
| 13 | 2724321600 |
| 14 | 27744837120 |
| 15 | 414096883200 |
| 16 | 8689288608000 |
| 17 | 111399326438400 |
| 18 | 2114134793971200 |
| 19 | 48501156601497600 |
| 20 | 759659036405068800 |
| 21 | 17279306372135808000 |
| 22 | 434100706059205785600 |