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 | 3 |
| 3 | 13 |
| 4 | 67 |
| 5 | 381 |
| 6 | 2307 |
| 7 | 14589 |
| 8 | 95235 |
| 9 | 636925 |
| 10 | 4341763 |
| 11 | 30056445 |
| 12 | 210731011 |
| 13 | 1493303293 |
| 14 | 10678370307 |
| 15 | 76957679613 |
| 16 | 558403682307 |
| 17 | 4075996839933 |
| 18 | 29909606989827 |
| 19 | 220510631755773 |
| 20 | 1632599134961667 |
| 21 | 12133359132082173 |