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 | 0 |
| 1 | 1 |
| 2 | -3 |
| 3 | 8 |
| 4 | -16 |
| 5 | 29 |
| 6 | -191 |
| 7 | 1980 |
| 8 | -14456 |
| 9 | 85713 |
| 10 | -657171 |
| 11 | 7877880 |
| 12 | -97759608 |
| 13 | 1100545341 |
| 14 | -13021637695 |
| 15 | 185198054748 |
| 16 | -2933940050000 |
| 17 | 46990261427073 |
| 18 | -774002505048195 |
| 19 | 13811029423532424 |
| 20 | -266175983849182016 |