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 | 3 |
| 4 | 7 |
| 5 | 25 |
| 6 | 90 |
| 7 | 350 |
| 8 | 1701 |
| 9 | 6951 |
| 10 | 42525 |
| 11 | 179487 |
| 12 | 1323652 |
| 13 | 5715424 |
| 14 | 49329280 |
| 15 | 216627840 |
| 16 | 2141764053 |
| 17 | 9528822303 |
| 18 | 106175395755 |
| 19 | 477297033785 |
| 20 | 5917584964655 |
| 21 | 26826851689001 |
| 22 | 366282500870286 |
| 23 | 1672162773483930 |
| 24 | 24930204590758260 |
| 25 | 114485073343744260 |