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 | 0 |
| 1 | 1 |
| 2 | 21 |
| 3 | 740 |
| 4 | 37310 |
| 5 | 2460024 |
| 6 | 200770416 |
| 7 | 19551774528 |
| 8 | 2213488134000 |
| 9 | 285711909912000 |
| 10 | 41419784380740480 |
| 11 | 6663725042739448320 |
| 12 | 1178209566488368028160 |
| 13 | 227096910697908706560000 |