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 | 9 |
| 2 | 65 |
| 3 | 585 |
| 4 | 4097 |
| 5 | 36873 |
| 6 | 266305 |
| 7 | 2396745 |
| 8 | 16777217 |
| 9 | 150994953 |
| 10 | 1090519105 |
| 11 | 9814671945 |
| 12 | 68736258049 |
| 13 | 618626322441 |
| 14 | 4467856773185 |
| 15 | 40210710958665 |
| 16 | 281474976710657 |
| 17 | 2533274790395913 |
| 18 | 18295873486192705 |
| 19 | 164662861375734345 |