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 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 9 |
| 5 | 23 |
| 6 | 63 |
| 7 | 177 |
| 8 | 514 |
| 9 | 1526 |
| 10 | 4624 |
| 11 | 14230 |
| 12 | 44357 |
| 13 | 139779 |
| 14 | 444557 |
| 15 | 1425151 |
| 16 | 4600338 |
| 17 | 14939849 |
| 18 | 48778197 |
| 19 | 160019884 |
| 20 | 527200711 |
| 21 | 1743607825 |
| 22 | 5786756469 |
| 23 | 19266336882 |
| 24 | 64331275266 |
| 25 | 215377539119 |
| 26 | 722840378041 |
| 27 | 2431459847363 |