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 | 18 |
| 3 | 108 |
| 4 | 180 |
| 5 | -5040 |
| 6 | 162000 |
| 7 | 14565600 |
| 8 | 563253408 |
| 9 | 17544639744 |
| 10 | 750412309248 |
| 11 | 56646776913408 |
| 12 | 4973976625190400 |
| 13 | 421817449494804480 |