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 | 1 |
| 3 | 3 |
| 4 | 13 |
| 5 | 75 |
| 6 | 525 |
| 7 | 4347 |
| 8 | 41245 |
| 9 | 441675 |
| 10 | 5259885 |
| 11 | 68958747 |
| 12 | 986533053 |
| 13 | 15292855019 |
| 14 | 255321427725 |
| 15 | 4567457001915 |
| 16 | 87156877087069 |
| 17 | 1767115200924299 |
| 18 | 37936303950503853 |
| 19 | 859663073472084315 |
| 20 | 20505904049009202685 |
| 21 | 513593410566661282347 |
| 22 | 13476082013068430626893 |