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 | 4 |
| 1 | -9 |
| 2 | 27 |
| 3 | -81 |
| 4 | 243 |
| 5 | -729 |
| 6 | 2187 |
| 7 | -6561 |
| 8 | 19683 |
| 9 | -59049 |
| 10 | 177147 |
| 11 | -531441 |
| 12 | 1594323 |
| 13 | -4782969 |
| 14 | 14348907 |
| 15 | -43046721 |
| 16 | 129140163 |
| 17 | -387420489 |
| 18 | 1162261467 |
| 19 | -3486784401 |
| 20 | 10460353203 |
| 21 | -31381059609 |
| 22 | 94143178827 |
| 23 | -282429536481 |
| 24 | 847288609443 |
| 25 | -2541865828329 |
| 26 | 7625597484987 |