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) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 6 |
| 4 | 0 |
| 5 | 540 |
| 6 | 0 |
| 7 | 156240 |
| 8 | 0 |
| 9 | 96480720 |
| 10 | 0 |
| 11 | 104661849600 |
| 12 | 0 |
| 13 | 177947471782080 |
| 14 | 0 |
| 15 | 439942718370355200 |
| 16 | 0 |
| 17 | 1499983925770422892800 |
| 18 | 0 |
| 19 | 6780179728814814933811200 |
| 20 | 0 |
| 21 | 39412342523061395825857920000 |
| 22 | 0 |