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 | 5 |
| 2 | 55 |
| 3 | 485 |
| 4 | 4380 |
| 5 | 39570 |
| 6 | 421800 |
| 7 | 4265100 |
| 8 | 49455000 |
| 9 | 594001800 |
| 10 | 7784683200 |
| 11 | 107814672000 |
| 12 | 1624964544000 |
| 13 | 25881953328000 |
| 14 | 443107288512000 |
| 15 | 8028628336512000 |
| 16 | 154539996629760000 |
| 17 | 3135393617489280000 |
| 18 | 67045955961922560000 |
| 19 | 1503619681171829760000 |
| 20 | 35321502985569884160000 |