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 | 0 |
| 3 | 6 |
| 4 | 6 |
| 5 | 20 |
| 6 | 120 |
| 7 | 7 |
| 8 | 1689 |
| 9 | 6636 |
| 10 | 36540 |
| 11 | 64020 |
| 12 | 963996 |
| 13 | 2894892 |
| 14 | 19555965 |
| 15 | 176079995 |
| 16 | 955611188 |
| 17 | 6684303780 |
| 18 | 42462792168 |
| 19 | 292378003753 |
| 20 | 1886275214112 |
| 21 | 13384059605364 |
| 22 | 87399249887334 |
| 23 | 624073002367892 |
| 24 | 5080120229014734 |
| 25 | 37587589611771480 |