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 | 0 |
| 3 | 0 |
| 4 | 24 |
| 5 | 120 |
| 6 | 720 |
| 7 | 5040 |
| 8 | 80640 |
| 9 | 1088640 |
| 10 | 14515200 |
| 11 | 199584000 |
| 12 | 3353011200 |
| 13 | 62270208000 |
| 14 | 1220496076800 |
| 15 | 24845812992000 |
| 16 | 543992537088000 |
| 17 | 12804747411456000 |
| 18 | 320118685286400000 |
| 19 | 8393511928209408000 |