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 | 0 |
| 5 | 1 |
| 6 | 6 |
| 7 | 42 |
| 8 | 336 |
| 9 | 3024 |
| 10 | 27216 |
| 11 | 299376 |
| 12 | 3592512 |
| 13 | 46702656 |
| 14 | 653837184 |
| 15 | 9880206336 |
| 16 | 158083301376 |
| 17 | 2687416123392 |
| 18 | 48373490221056 |
| 19 | 919096314200064 |
| 20 | 18375168222867456 |
| 21 | 385878532680216576 |
| 22 | 8489327718964764672 |
| 23 | 195254537536189587456 |
| 24 | 4686108900868550098944 |