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 | 3 |
| 1 | 13 |
| 2 | 84 |
| 3 | 800 |
| 4 | 4356 |
| 5 | 51792 |
| 6 | 351120 |
| 7 | 3100240 |
| 8 | 17041416 |
| 9 | 211053040 |
| 10 | 1494039792 |
| 11 | 12611914848 |
| 12 | 73234343952 |
| 13 | 794382536272 |
| 14 | 5936210280000 |
| 15 | 60037292774400 |
| 16 | 282937726148616 |
| 17 | 3264911394064320 |
| 18 | 24128875076496960 |
| 19 | 208532141890460960 |
| 20 | 1225825603154905104 |