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 | 360 |
| 7 | 7560 |
| 8 | 95760 |
| 9 | 952560 |
| 10 | 8217720 |
| 11 | 64615680 |
| 12 | 476514720 |
| 13 | 3355679880 |
| 14 | 22837094280 |
| 15 | 151449674040 |
| 16 | 984573560880 |
| 17 | 6302070915840 |
| 18 | 39847410373680 |
| 19 | 249509384858160 |
| 20 | 1550188402338240 |
| 21 | 9570844671217200 |