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 | 6 |
| 5 | -18 |
| 6 | 44 |
| 7 | -56 |
| 8 | -300 |
| 9 | 2024 |
| 10 | -22022 |
| 11 | -130456 |
| 12 | -4241064 |
| 13 | -103538532 |
| 14 | -2893308780 |
| 15 | -88314189664 |
| 16 | -2924814872208 |
| 17 | -104538530634844 |
| 18 | -4010605941377292 |
| 19 | -164409679858874856 |
| 20 | -7172735079437282200 |
| 21 | -331847552362286195156 |
| 22 | -16229743737669369558956 |
| 23 | -836695536495554388520400 |