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) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 9 |
| 4 | 27 |
| 5 | 15 |
| 6 | 81 |
| 7 | 243 |
| 8 | 45 |
| 9 | 729 |
| 10 | 2187 |
| 11 | 135 |
| 12 | 105 |
| 13 | 6561 |
| 14 | 225 |
| 15 | 19683 |
| 16 | 405 |
| 17 | 59049 |
| 18 | 177147 |
| 19 | 1215 |
| 20 | 315 |
| 21 | 675 |