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 | 2 |
| 4 | -7 |
| 5 | 15 |
| 6 | -78 |
| 7 | 293 |
| 8 | -1629 |
| 9 | 8992 |
| 10 | -58105 |
| 11 | 404669 |
| 12 | -3097456 |
| 13 | 25617669 |
| 14 | -228373197 |
| 15 | 2180640110 |
| 16 | -22212371403 |
| 17 | 240392198791 |
| 18 | -2754699284494 |
| 19 | 33320193986081 |
| 20 | -424246016043385 |
| 21 | 5671750867032228 |
| 22 | -79436475109286061 |
| 23 | 1163129092965592997 |