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 | 3 |
| 2 | -9 |
| 3 | -81 |
| 4 | -243 |
| 5 | -1215 |
| 6 | -5103 |
| 7 | -15309 |
| 8 | -59049 |
| 9 | -216513 |
| 10 | -649539 |
| 11 | -2302911 |
| 12 | -7971615 |
| 13 | -23914845 |
| 14 | -81310473 |
| 15 | -272629233 |
| 16 | -817887699 |
| 17 | -2711943423 |
| 18 | -8910671247 |
| 19 | -26732013741 |
| 20 | -87169610025 |
| 21 | -282429536481 |
| 22 | -847288609443 |