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 | 45 |
| 2 | 252 |
| 3 | 28350 |
| 4 | 1496880 |
| 5 | 3405402000 |
| 6 | 17513496000 |
| 7 | 7815397590000 |
| 8 | 5543722023840000 |
| 9 | 235212205868640000 |
| 10 | 206559082608278400000 |
| 11 | 516914104227216696000000 |
| 12 | 572581776990147724800000 |