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 | -2 |
| 3 | -3 |
| 4 | 0 |
| 5 | 55 |
| 6 | 572 |
| 7 | 4865 |
| 8 | 40912 |
| 9 | 351675 |
| 10 | 2978196 |
| 11 | 23418373 |
| 12 | 148849544 |
| 13 | 84185855 |
| 14 | -27459134420 |
| 15 | -881482705719 |
| 16 | -21652972750464 |
| 17 | -487503384038525 |
| 18 | -10785437160748156 |
| 19 | -242968902040697011 |
| 20 | -5627949704687484872 |
| 21 | -133358411031825299385 |