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 | 0 |
| 4 | -3 |
| 5 | 12 |
| 6 | 117 |
| 7 | 336 |
| 8 | -903 |
| 9 | -2096 |
| 10 | 111529 |
| 11 | 1043328 |
| 12 | 687093 |
| 13 | -29488704 |
| 14 | 320199453 |
| 15 | 8894706432 |
| 16 | 44530596081 |
| 17 | -389860902656 |
| 18 | 254346923089 |
| 19 | 170568226222080 |
| 20 | 2006766293627373 |
| 21 | -6327905330549760 |
| 22 | -141849542553657147 |