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 | 0 |
| 1 | 1 |
| 2 | 12 |
| 3 | 135 |
| 4 | 1680 |
| 5 | 23625 |
| 6 | 374220 |
| 7 | 6621615 |
| 8 | 129729600 |
| 9 | 2791213425 |
| 10 | 65472907500 |
| 11 | 1663666579575 |
| 12 | 45537716624400 |
| 13 | 1336089255125625 |
| 14 | 41837777148667500 |
| 15 | 1392813754566609375 |
| 16 | 49126088694402720000 |
| 17 | 1830138702650463830625 |
| 18 | 71812362934450726087500 |