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 | 1 |
| 3 | 1 |
| 4 | 4 |
| 5 | 16 |
| 6 | 46 |
| 7 | 106 |
| 8 | 316 |
| 9 | 1324 |
| 10 | 5356 |
| 11 | 18316 |
| 12 | 63856 |
| 13 | 272416 |
| 14 | 1264264 |
| 15 | 5409496 |
| 16 | 22302736 |
| 17 | 101343376 |
| 18 | 507711376 |
| 19 | 2495918224 |
| 20 | 11798364736 |
| 21 | 58074029056 |
| 22 | 309240315616 |
| 23 | 1670570920096 |
| 24 | 8792390355904 |
| 25 | 46886941456576 |
| 26 | 264381946998976 |
| 27 | 1533013006902976 |