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 | 4 |
| 2 | -7 |
| 3 | 36 |
| 4 | -282 |
| 5 | 2952 |
| 6 | -38640 |
| 7 | 606960 |
| 8 | -11123280 |
| 9 | 232968960 |
| 10 | -5489285760 |
| 11 | 143711366400 |
| 12 | -4138653657600 |
| 13 | 130021631308800 |
| 14 | -4425213650457600 |
| 15 | 162195036421017600 |
| 16 | -6369481772349696000 |
| 17 | 266808316331741184000 |
| 18 | -11874725090839683072000 |