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 | 6 |
| 4 | 72 |
| 5 | 720 |
| 6 | 10080 |
| 7 | 156240 |
| 8 | 2822400 |
| 9 | 56972160 |
| 10 | 1280966400 |
| 11 | 31654022400 |
| 12 | 853580851200 |
| 13 | 24932991283200 |
| 14 | 784343085926400 |
| 15 | 26435945023488000 |
| 16 | 950417730662400000 |
| 17 | 36304660098330624000 |
| 18 | 1468365202287599616000 |