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 | 4 |
| 3 | 40 |
| 4 | 1344 |
| 5 | 203136 |
| 6 | 495598592 |
| 7 | 309065330371840 |
| 8 | 14369391920653644779049472 |