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 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | -6 |
| 5 | 35 |
| 6 | -224 |
| 7 | 1603 |
| 8 | -12810 |
| 9 | 113589 |
| 10 | -1109472 |
| 11 | 11852841 |
| 12 | -137611110 |
| 13 | 1726238787 |
| 14 | -23277264192 |
| 15 | 335861699355 |
| 16 | -5164348236138 |
| 17 | 84316474011861 |
| 18 | -1456893047937600 |
| 19 | 26562992204112273 |
| 20 | -509679388313669574 |
| 21 | 10266675502780006947 |
| 22 | -216625348636705401120 |