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) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 1 |
| 4 | 4 |
| 5 | 18 |
| 6 | 84 |
| 7 | 405 |
| 8 | 2004 |
| 9 | 10126 |
| 10 | 52048 |
| 11 | 271338 |
| 12 | 1431400 |
| 13 | 7627348 |
| 14 | 40994652 |
| 15 | 221984157 |
| 16 | 1209902388 |
| 17 | 6632482710 |
| 18 | 36544255968 |
| 19 | 202275553662 |
| 20 | 1124212840440 |
| 21 | 6271377279804 |
| 22 | 35102535960360 |
| 23 | 197081848211394 |
| 24 | 1109621661515016 |
| 25 | 6263608341803916 |