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) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 20 |
| 4 | 220 |
| 5 | 1540 |
| 6 | 30800 |
| 7 | 277200 |
| 8 | 7207200 |
| 9 | 129729600 |
| 10 | 3632428800 |
| 11 | 47221574400 |
| 12 | 2597186592000 |
| 13 | 38957798880000 |
| 14 | 1402480759680000 |
| 15 | 49086826588800000 |
| 16 | 2797949115561600000 |
| 17 | 53161033195670400000 |
| 18 | 3827594390088268800000 |
| 19 | 80379482191853644800000 |