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 | 0 |
| 2 | 0 |
| 3 | 6 |
| 4 | -24 |
| 5 | 0 |
| 6 | 360 |
| 7 | 0 |
| 8 | -20160 |
| 9 | 60480 |
| 10 | 1814400 |
| 11 | -19958400 |
| 12 | -59875200 |
| 13 | 2075673600 |
| 14 | 21794572800 |
| 15 | -860885625600 |
| 16 | 3487131648000 |
| 17 | 148203095040000 |
| 18 | -524638956441600 |
| 19 | -71973351075225600 |
| 20 | 942749528168448000 |
| 21 | 19878836825143296000 |
| 22 | -437111394135736320000 |