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 | -1 |
| 4 | -2 |
| 5 | -14 |
| 6 | -98 |
| 7 | -822 |
| 8 | -7948 |
| 9 | -86590 |
| 10 | -1046916 |
| 11 | -13892842 |
| 12 | -200653570 |
| 13 | -3133064534 |
| 14 | -52596852266 |
| 15 | -944892417438 |
| 16 | -18091297436248 |
| 17 | -367841660947508 |
| 18 | -7916992964642992 |
| 19 | -179849204152350892 |
| 20 | -4300928485463624458 |
| 21 | -108013481381638292266 |