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 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 1 |
| 6 | 15 |
| 7 | 465 |
| 8 | 19355 |
| 9 | 1024380 |
| 10 | 66462480 |
| 11 | 5188446900 |
| 12 | 480413448900 |
| 13 | 52113339432000 |
| 14 | 6551243302804200 |
| 15 | 945313572845842200 |
| 16 | 155243683741953807000 |
| 17 | 28797215441570535960000 |
| 18 | 5993001571565164940784000 |
| 19 | 1390759438984816084192008000 |