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 | 3 |
| 3 | 14 |
| 4 | 82 |
| 5 | 514 |
| 6 | 2508 |
| 7 | -12328 |
| 8 | -820752 |
| 9 | -22232232 |
| 10 | -498433320 |
| 11 | -9865850688 |
| 12 | -159373484448 |
| 13 | -1136343398880 |
| 14 | 65056426313760 |
| 15 | 4663237803223680 |
| 16 | 210535052582008320 |
| 17 | 7821007002377349120 |
| 18 | 242387957802121971840 |
| 19 | 5333182310844833642496 |