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 | -9 |
| 5 | 72 |
| 6 | -710 |
| 7 | 8563 |
| 8 | -121814 |
| 9 | 1997502 |
| 10 | -37097739 |
| 11 | 769687954 |
| 12 | -17644355410 |
| 13 | 442894514285 |
| 14 | -12081668234012 |
| 15 | 355889274553166 |
| 16 | -11258683640579857 |
| 17 | 380701046875217492 |
| 18 | -13702507978018209458 |
| 19 | 523049811008797507683 |
| 20 | -21105565578064063658754 |