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 | 5 |
| 3 | 32 |
| 4 | 270 |
| 5 | 2904 |
| 6 | 38400 |
| 7 | 605520 |
| 8 | 11113200 |
| 9 | 232888320 |
| 10 | 5488560000 |
| 11 | 143704108800 |
| 12 | 4138573824000 |
| 13 | 130020673305600 |
| 14 | 4425201196416000 |
| 15 | 162194862064435200 |
| 16 | 6369479157000960000 |
| 17 | 266808274486161408000 |
| 18 | 11874724379464826880000 |
| 19 | 559591797303082672128000 |