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 | 12 |
| 2 | 120 |
| 3 | 1120 |
| 4 | 10080 |
| 5 | 88704 |
| 6 | 768768 |
| 7 | 6589440 |
| 8 | 56010240 |
| 9 | 472975360 |
| 10 | 3972993024 |
| 11 | 33228668928 |
| 12 | 276905574400 |
| 13 | 2300446310400 |
| 14 | 19060840857600 |
| 15 | 157569617756160 |
| 16 | 1299949346488320 |
| 17 | 10705465206374400 |
| 18 | 88022713919078400 |
| 19 | 722712809019801600 |
| 20 | 5926245033962373120 |