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 | -1 |
| 3 | 9 |
| 4 | -6 |
| 5 | 1 |
| 6 | 27 |
| 7 | -27 |
| 8 | 9 |
| 9 | -1 |
| 10 | 81 |
| 11 | -108 |
| 12 | 54 |
| 13 | -12 |
| 14 | 1 |
| 15 | 243 |
| 16 | -405 |
| 17 | 270 |
| 18 | -90 |
| 19 | 15 |
| 20 | -1 |
| 21 | 729 |
| 22 | -1458 |
| 23 | 1215 |
| 24 | -540 |
| 25 | 135 |
| 26 | -18 |
| 27 | 1 |
| 28 | 2187 |
| 29 | -5103 |
| 30 | 5103 |
| 31 | -2835 |
| 32 | 945 |
| 33 | -189 |
| 34 | 21 |
| 35 | -1 |
| 36 | 6561 |
| 37 | -17496 |
| 38 | 20412 |
| 39 | -13608 |
| 40 | 5670 |
| 41 | -1512 |
| 42 | 252 |
| 43 | -24 |
| 44 | 1 |
| 45 | 19683 |
| 46 | -59049 |
| 47 | 78732 |
| 48 | -61236 |
| 49 | 30618 |
| 50 | -10206 |
| 51 | 2268 |
| 52 | -324 |
| 53 | 27 |
| 54 | -1 |