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 | 15 |
| 3 | 87 |
| 4 | 543 |
| 5 | 3543 |
| 6 | 23823 |
| 7 | 163719 |
| 8 | 1143999 |
| 9 | 8099511 |
| 10 | 57959535 |
| 11 | 418441191 |
| 12 | 3043608351 |
| 13 | 22280372247 |
| 14 | 164008329423 |
| 15 | 1213166815047 |
| 16 | 9012417249663 |
| 17 | 67208553680247 |
| 18 | 502920171632943 |
| 19 | 3775020828459687 |
| 20 | 28415858155984863 |
| 21 | 214444848602732247 |
| 22 | 1622146752543427983 |