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 | 0 |
| 3 | 2 |
| 4 | 0 |
| 5 | 72 |
| 6 | 0 |
| 7 | 2704 |
| 8 | 0 |
| 9 | 268128 |
| 10 | 0 |
| 11 | 17621496 |
| 12 | 0 |
| 13 | 4974281208 |
| 14 | 0 |
| 15 | 549790303712 |
| 16 | 0 |
| 17 | 245357774621280 |
| 18 | 0 |
| 19 | 67684833350266496 |
| 20 | 0 |
| 21 | 36434223374991414336 |
| 22 | 0 |
| 23 | 10781900341537812480000 |
| 24 | 0 |
| 25 | 14585451990785851336761600 |
| 26 | 0 |
| 27 | 4706112122106541811177554944 |
| 28 | 0 |
| 29 | 5607912482098966721098538956800 |
| 30 | 0 |