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 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | -4 |
| 4 | 8 |
| 5 | 57 |
| 6 | -771 |
| 7 | 4168 |
| 8 | 22504 |
| 9 | -943255 |
| 10 | 13349105 |
| 11 | -48905364 |
| 12 | -3284972544 |
| 13 | 117005181841 |
| 14 | -2071095992867 |
| 15 | -2153841382168 |
| 16 | 1791029813641424 |
| 17 | -79511121545541327 |
| 18 | 1867021096818903489 |
| 19 | 8850156160819959100 |
| 20 | -3592582141732300745000 |