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 | 2 |
| 2 | 4 |
| 3 | 20 |
| 4 | 48 |
| 5 | 280 |
| 6 | 720 |
| 7 | 5580 |
| 8 | 14976 |
| 9 | 99360 |
| 10 | 291200 |
| 11 | 2219460 |
| 12 | 5184000 |
| 13 | 46950120 |
| 14 | 139991040 |
| 15 | 876960000 |
| 16 | 2752708608 |
| 17 | 22384531584 |
| 18 | 55435726080 |
| 19 | 499226178000 |
| 20 | 1280348160000 |
| 21 | 10957459615200 |
| 22 | 34031246515200 |
| 23 | 259121741860800 |
| 24 | 630789120000000 |
| 25 | 5255180000000000 |