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 | -8 |
| 4 | 13 |
| 5 | -47 |
| 6 | 15481 |
| 7 | -15788 |
| 8 | 451939 |
| 9 | -23252857 |
| 10 | 186846623 |
| 11 | -831520891 |
| 12 | 1108990801 |
| 13 | -143356511198507 |
| 14 | 920716137922619 |
| 15 | -13390469094133441 |
| 16 | 929480267163260699 |
| 17 | -118186323448146684881 |
| 18 | 69875813865886026036091 |
| 19 | -155759565768613453511731 |