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 | 2 |
| 2 | -1 |
| 3 | 8 |
| 4 | -19 |
| 5 | 62 |
| 6 | -181 |
| 7 | 548 |
| 8 | -1639 |
| 9 | 4922 |
| 10 | -14761 |
| 11 | 44288 |
| 12 | -132859 |
| 13 | 398582 |
| 14 | -1195741 |
| 15 | 3587228 |
| 16 | -10761679 |
| 17 | 32285042 |
| 18 | -96855121 |
| 19 | 290565368 |
| 20 | -871696099 |
| 21 | 2615088302 |
| 22 | -7845264901 |
| 23 | 23535794708 |
| 24 | -70607384119 |
| 25 | 211822152362 |
| 26 | -635466457081 |
| 27 | 1906399371248 |