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 | 18 |
| 4 | 72 |
| 5 | 450 |
| 6 | 2700 |
| 7 | 22050 |
| 8 | 176400 |
| 9 | 1587600 |
| 10 | 15876000 |
| 11 | 192099600 |
| 12 | 2305195200 |
| 13 | 32464832400 |
| 14 | 454507653600 |
| 15 | 6817614804000 |
| 16 | 109081836864000 |
| 17 | 1970290678356000 |
| 18 | 35465232210408000 |
| 19 | 711274934886516000 |