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 | 2 |
| 3 | 6 |
| 4 | 48 |
| 5 | 2880 |
| 6 | 9953280 |
| 7 | 115579079884800 |
| 8 | 15266884236590834264309760000 |
| 9 | 262212473580148912869121218589990322256745385164800000000 |