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 | 1 |
| 4 | 12 |
| 5 | 15 |
| 6 | 900 |
| 7 | 6615 |
| 8 | 90720 |
| 9 | 1995840 |
| 10 | 1360800 |
| 11 | 197920800 |
| 12 | 359251200 |
| 13 | 1297296000 |
| 14 | 7264857600 |
| 15 | 119870150400 |
| 16 | 2615348736000 |
| 17 | 29640619008000 |
| 18 | 533531142144000 |
| 19 | 101370917007360000 |
| 20 | 101370917007360000 |
| 21 | 425757851430912000 |
| 22 | 3325168819675422720000 |