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 | 60480 |
| 9 | 725760 |
| 10 | 9072000 |
| 11 | 119750400 |
| 12 | 1756339200 |
| 13 | 28021593600 |
| 14 | 479480601600 |
| 15 | 8717829120000 |
| 16 | 168254102016000 |
| 17 | 3438311804928000 |
| 18 | 74160828758016000 |
| 19 | 1682757222322176000 |
| 20 | 40061786401308672000 |
| 21 | 998402161605488640000 |