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 | 0 |
| 3 | 2 |
| 4 | 4 |
| 5 | -36 |
| 6 | -56 |
| 7 | 944 |
| 8 | 1744 |
| 9 | -41104 |
| 10 | -86208 |
| 11 | 2650592 |
| 12 | 6199744 |
| 13 | -237023424 |
| 14 | -608357504 |
| 15 | 28021573376 |
| 16 | 77889982720 |
| 17 | -4225816615168 |
| 18 | -12588540708864 |
| 19 | 790713657219584 |
| 20 | 2503565961032704 |
| 21 | -179579770991391744 |