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 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 9 |
| 5 | 105 |
| 6 | 225 |
| 7 | 945 |
| 8 | 36225 |
| 9 | 76545 |
| 10 | 2253825 |
| 11 | 9511425 |
| 12 | 89345025 |
| 13 | 1526349825 |
| 14 | 26434433025 |
| 15 | 287969306625 |
| 16 | 12057038618625 |
| 17 | 179439357722625 |
| 18 | 5870438207258625 |
| 19 | 37882306735898625 |
| 20 | 1984203913277210625 |
| 21 | 11715811945983770625 |
| 22 | 982443713208463130625 |
| 23 | 15594453174317362970625 |