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 | 2 |
| 3 | 12 |
| 4 | 84 |
| 5 | 720 |
| 6 | 7440 |
| 7 | 90720 |
| 8 | 1280160 |
| 9 | 20563200 |
| 10 | 370863360 |
| 11 | 7424524800 |
| 12 | 163419379200 |
| 13 | 3923023104000 |
| 14 | 102011054745600 |
| 15 | 2856483889459200 |
| 16 | 85697132032512000 |
| 17 | 2742350070620160000 |
| 18 | 93240613775941632000 |