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 | 1 |
| 2 | 0 |
| 3 | -2 |
| 4 | 8 |
| 5 | 0 |
| 6 | -320 |
| 7 | 2800 |
| 8 | 0 |
| 9 | -344960 |
| 10 | 4659200 |
| 11 | 0 |
| 12 | -1172864000 |
| 13 | 21423001600 |
| 14 | 0 |
| 15 | -9117844736000 |
| 16 | 209945415680000 |
| 17 | 0 |
| 18 | -135381758640128000 |
| 19 | 3761801958154240000 |
| 20 | 0 |
| 21 | -3421097040836034560000 |
| 22 | 111349337961365504000000 |
| 23 | 0 |
| 24 | -135776499356700539617280000 |