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 | 0 |
| 5 | 0 |
| 6 | 120 |
| 7 | 5040 |
| 8 | 161280 |
| 9 | 4898880 |
| 10 | 151200000 |
| 11 | 4870182240 |
| 12 | 165589522560 |
| 13 | 5970883913280 |
| 14 | 228632817853440 |
| 15 | 9292843409850000 |
| 16 | 400385970127503360 |
| 17 | 18252778818295082880 |
| 18 | 878619947953407528960 |
| 19 | 44562094805330883023040 |
| 20 | 2376296054962478899200000 |