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 | 2 |
| 2 | 20 |
| 3 | 712 |
| 4 | 91920 |
| 5 | 44874784 |
| 6 | 85939843136 |
| 7 | 660213878210688 |
| 8 | 20540390859740217600 |
| 9 | 2592165941692975372042752 |
| 10 | 1324271564605167892188248409088 |
| 11 | 2730585827960928853182474922961668096 |