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 | -19 |
| 5 | -248 |
| 6 | -2355 |
| 7 | -14504 |
| 8 | 69113 |
| 9 | 4886848 |
| 10 | 117560921 |
| 11 | 1925294976 |
| 12 | 14523966437 |
| 13 | -478472693632 |
| 14 | -28832809713435 |
| 15 | -921278399444480 |
| 16 | -18983574162924687 |
| 17 | -55161522627854336 |
| 18 | 18306724696454977713 |
| 19 | 1118400460045234098176 |
| 20 | 41755736397548337559133 |