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 | 1 |
| 2 | -2 |
| 3 | 8 |
| 4 | -32 |
| 5 | 176 |
| 6 | -1056 |
| 7 | 7664 |
| 8 | -61312 |
| 9 | 559744 |
| 10 | -5597440 |
| 11 | 61925632 |
| 12 | -743107584 |
| 13 | 9682766848 |
| 14 | -135558735872 |
| 15 | 2035284795392 |
| 16 | -32564556726272 |
| 17 | 553807329689600 |
| 18 | -9968531934412800 |
| 19 | 189431195638956032 |
| 20 | -3788623912779120640 |