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 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 1 |
| 5 | 3 |
| 6 | 9 |
| 7 | 28 |
| 8 | 93 |
| 9 | 321 |
| 10 | 1168 |
| 11 | 4404 |
| 12 | 17328 |
| 13 | 70408 |
| 14 | 296436 |
| 15 | 1284768 |
| 16 | 5740804 |
| 17 | 26332788 |
| 18 | 124066608 |
| 19 | 598625296 |
| 20 | 2958281328 |
| 21 | 14941136784 |
| 22 | 77111251408 |
| 23 | 406028059968 |
| 24 | 2180584156176 |
| 25 | 11930067296848 |
| 26 | 66468429865344 |
| 27 | 376770132276288 |
| 28 | 2172036623279488 |