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 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 4 |
| 5 | 10 |
| 6 | 46 |
| 7 | 126 |
| 8 | 316 |
| 9 | 1296 |
| 10 | 5356 |
| 11 | 17380 |
| 12 | 63856 |
| 13 | 296088 |
| 14 | 1264264 |
| 15 | 4940040 |
| 16 | 22302736 |
| 17 | 110455936 |
| 18 | 507711376 |
| 19 | 2313783216 |
| 20 | 11798364736 |
| 21 | 61878663840 |
| 22 | 309240315616 |
| 23 | 1587272962528 |
| 24 | 8792390355904 |
| 25 | 48793502304000 |