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 | 0 |
| 5 | 0 |
| 6 | 720 |
| 7 | 15120 |
| 8 | 191520 |
| 9 | 1905120 |
| 10 | 16435440 |
| 11 | 129230640 |
| 12 | 953028720 |
| 13 | 6711344640 |
| 14 | 45674173440 |
| 15 | 302899156560 |
| 16 | 1969146930240 |
| 17 | 12604139926560 |
| 18 | 79694818842240 |
| 19 | 499018753280880 |
| 20 | 3100376788241040 |