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) |
|---|---|
| 1 | 1 |
| 2 | -1 |
| 3 | 2 |
| 4 | -5 |
| 5 | 9 |
| 6 | 53 |
| 7 | -1107 |
| 8 | 12983 |
| 9 | -116470 |
| 10 | 560049 |
| 11 | 8370713 |
| 12 | -346902877 |
| 13 | 7551856337 |
| 14 | -117404648467 |
| 15 | 913399734614 |
| 16 | 22560135521007 |
| 17 | -1393700803877939 |
| 18 | 44331044030953865 |
| 19 | -979905458659247779 |
| 20 | 10462396536804802459 |
| 21 | 367799071887303276422 |
| 22 | -30046998012662824941947 |