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 | 15 |
| 2 | 128 |
| 3 | 816 |
| 4 | 4320 |
| 5 | 20064 |
| 6 | 84480 |
| 7 | 329472 |
| 8 | 1208064 |
| 9 | 4209920 |
| 10 | 14057472 |
| 11 | 45260800 |
| 12 | 141213696 |
| 13 | 428654592 |
| 14 | 1270087680 |
| 15 | 3683254272 |
| 16 | 10478223360 |
| 17 | 29297934336 |
| 18 | 80648077312 |
| 19 | 218864025600 |
| 20 | 586290298880 |
| 21 | 1551944908800 |
| 22 | 4063273943040 |