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 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 2 |
| 5 | 4 |
| 6 | 24 |
| 7 | 48 |
| 8 | 0 |
| 9 | 4032 |
| 10 | 17280 |
| 11 | 5400 |
| 12 | 0 |
| 13 | 518400 |
| 14 | 415134720 |
| 15 | 0 |
| 16 | 0 |
| 17 | 1797120 |
| 18 | 6467044147200 |
| 19 | 39086530560 |
| 20 | 0 |
| 21 | 0 |
| 22 | 1738201006080000 |
| 23 | 10247897088 |
| 24 | 0 |
| 25 | 9632530575360000 |
| 26 | 706822057112371200000 |
| 27 | 569299069913333760000 |
| 28 | 0 |
| 29 | 54538738974720000 |
| 30 | 0 |