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 | 0 |
| 3 | 4 |
| 4 | 126 |
| 5 | 4368 |
| 6 | 177100 |
| 7 | 8347680 |
| 8 | 450978066 |
| 9 | 27540584512 |
| 10 | 1878392407320 |
| 11 | 141629804643600 |
| 12 | 11703541346076580 |
| 13 | 1052134368066259632 |
| 14 | 102250849636865496528 |
| 15 | 10683770265451303535424 |
| 16 | 1194448077521704400002650 |
| 17 | 142288257910903254700704000 |
| 18 | 17993390003427864738863790640 |