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 | -14 |
| 5 | 146 |
| 6 | -1944 |
| 7 | 31620 |
| 8 | -608068 |
| 9 | 13502076 |
| 10 | -340052704 |
| 11 | 9579145016 |
| 12 | -298455813160 |
| 13 | 10191129869272 |
| 14 | -378469678855904 |
| 15 | 15187759126892976 |
| 16 | -654936026064200944 |
| 17 | 30203464484648818960 |
| 18 | -1483333523694819075328 |
| 19 | 77291514214052885054496 |