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 | 0 |
| 4 | 4 |
| 5 | 1380 |
| 6 | 75600 |
| 7 | 2340744 |
| 8 | 54275296 |
| 9 | 1055436228 |
| 10 | 18230184752 |
| 11 | 289150871152 |
| 12 | 4300858168200 |
| 13 | 60843411796440 |