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 | 7 |
| 2 | 42 |
| 3 | 258 |
| 4 | 1752 |
| 5 | 13320 |
| 6 | 113040 |
| 7 | 1063440 |
| 8 | 11007360 |
| 9 | 124467840 |
| 10 | 1527724800 |
| 11 | 20237817600 |
| 12 | 287879961600 |
| 13 | 4377595622400 |
| 14 | 70875950745600 |
| 15 | 1217444836608000 |
| 16 | 22115388911616000 |
| 17 | 423623726862336000 |
| 18 | 8534364149735424000 |