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 | 2 |
| 2 | 0 |
| 3 | -4 |
| 4 | 16 |
| 5 | -48 |
| 6 | 64 |
| 7 | 800 |
| 8 | -12288 |
| 9 | 127232 |
| 10 | -1150976 |
| 11 | 9266688 |
| 12 | -58726400 |
| 13 | 68777984 |
| 14 | 7510646784 |
| 15 | -207794409472 |
| 16 | 4241007640576 |
| 17 | -77359570944000 |
| 18 | 1321952191971328 |
| 19 | -21274345818161152 |
| 20 | 313768799799607296 |
| 21 | -3838962981483839488 |
| 22 | 21775623343518515200 |
| 23 | 859024717017756205056 |