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 | 0 |
| 2 | 0 |
| 3 | 2 |
| 4 | 6 |
| 5 | 24 |
| 6 | 100 |
| 7 | 480 |
| 8 | 1890 |
| 9 | 8960 |
| 10 | 47040 |
| 11 | 288000 |
| 12 | 1584000 |
| 13 | 10644480 |
| 14 | 74131200 |
| 15 | 615014400 |
| 16 | 3783780000 |
| 17 | 29520691200 |
| 18 | 230015385600 |
| 19 | 2199674880000 |
| 20 | 17239951872000 |
| 21 | 172890685440000 |
| 22 | 1660143513600000 |
| 23 | 19778694414336000 |
| 24 | 174145223476224000 |
| 25 | 2007117934991769600 |