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 | 0 |
| 1 | 12 |
| 2 | 120 |
| 3 | -828 |
| 4 | -28560 |
| 5 | -145668 |
| 6 | 3369960 |
| 7 | 58317492 |
| 8 | 13651680 |
| 9 | -9719139348 |
| 10 | -99498527400 |
| 11 | 647549275812 |
| 12 | 23290743888720 |
| 13 | 123471611274972 |
| 14 | -2701419604443960 |
| 15 | -47880898349909868 |
| 16 | -22269070348069440 |
| 17 | 7869181117654073292 |
| 18 | 82455284065364468280 |
| 19 | -505338768229893703548 |