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 | 0 |
| 4 | 24 |
| 5 | 60 |
| 6 | 240 |
| 7 | 1260 |
| 8 | 28224 |
| 9 | 241920 |
| 10 | 2181600 |
| 11 | 21621600 |
| 12 | 395176320 |
| 13 | 5915669760 |
| 14 | 87034409280 |
| 15 | 1321166246400 |
| 16 | 26242709391360 |
| 17 | 529649632512000 |
| 18 | 10741214992435200 |
| 19 | 221702803264051200 |
| 20 | 5187617452174233600 |
| 21 | 128491776028533657600 |