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 | 6 |
| 2 | 40 |
| 3 | 336 |
| 4 | 3456 |
| 5 | 42240 |
| 6 | 599040 |
| 7 | 9676800 |
| 8 | 175472640 |
| 9 | 3530096640 |
| 10 | 78033715200 |
| 11 | 1880240947200 |
| 12 | 49049763840000 |
| 13 | 1377317368627200 |
| 14 | 41421544567603200 |
| 15 | 1328346084409344000 |
| 16 | 45249466617298944000 |
| 17 | 1631723190138961920000 |
| 18 | 62098722550431350784000 |
| 19 | 2487305589722682753024000 |