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 | 1 |
| 3 | 3 |
| 4 | 9 |
| 5 | 21 |
| 6 | 99 |
| 7 | 225 |
| 8 | 729 |
| 9 | 2187 |
| 10 | 6561 |
| 11 | 19845 |
| 12 | 58563 |
| 13 | 177633 |
| 14 | 531441 |
| 15 | 1594323 |
| 16 | 4782969 |
| 17 | 14344533 |
| 18 | 43059843 |
| 19 | 129127041 |
| 20 | 387420489 |
| 21 | 1162261467 |