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 | 3 |
| 2 | 4 |
| 3 | 72 |
| 4 | 132 |
| 5 | 7020 |
| 6 | 17280 |
| 7 | 1920240 |
| 8 | 6022800 |
| 9 | 1154366640 |
| 10 | 4421511360 |
| 11 | 1303028052480 |
| 12 | 5906331224640 |
| 13 | 2481613890275520 |
| 14 | 13003380449579520 |
| 15 | 7385997122881977600 |
| 16 | 43944212734316294400 |
| 17 | 32440254625217626387200 |
| 18 | 216088204725662645376000 |