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 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 125 |
| 6 | 780 |
| 7 | 5670 |
| 8 | 47040 |
| 9 | 439110 |
| 10 | 4561200 |
| 11 | 52182900 |
| 12 | 651974400 |
| 13 | 8832874050 |
| 14 | 129001672800 |
| 15 | 2020822303500 |
| 16 | 33805804032000 |
| 17 | 601587281295000 |
| 18 | 11348960759136000 |
| 19 | 226275153994890000 |
| 20 | 4755046903326720000 |
| 21 | 105061084389756495000 |
| 22 | 2435176811445618240000 |