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 | 1 |
| 3 | 4 |
| 4 | -3 |
| 5 | 96 |
| 6 | -755 |
| 7 | 10368 |
| 8 | -147623 |
| 9 | 2492416 |
| 10 | -47137959 |
| 11 | 996741120 |
| 12 | -23260103339 |
| 13 | 594198429696 |
| 14 | -16492683271259 |
| 15 | 494278721929216 |
| 16 | -15908038836914895 |
| 17 | 547238863907586048 |
| 18 | -20038031401448021327 |
| 19 | 778147549666716155904 |
| 20 | -31943565308583934360019 |