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 | 7 |
| 2 | 21 |
| 3 | 63 |
| 4 | 189 |
| 5 | 567 |
| 6 | 1701 |
| 7 | 5103 |
| 8 | 15309 |
| 9 | 45927 |
| 10 | 137781 |
| 11 | 413343 |
| 12 | 1240029 |
| 13 | 3720087 |
| 14 | 11160261 |
| 15 | 33480783 |
| 16 | 100442349 |
| 17 | 301327047 |
| 18 | 903981141 |
| 19 | 2711943423 |
| 20 | 8135830269 |
| 21 | 24407490807 |
| 22 | 73222472421 |
| 23 | 219667417263 |
| 24 | 659002251789 |
| 25 | 1977006755367 |