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 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 24 |
| 5 | 178 |
| 6 | 1512 |
| 7 | 14152 |
| 8 | 142705 |
| 9 | 1528212 |
| 10 | 17211564 |
| 11 | 202460400 |
| 12 | 2474708496 |
| 13 | 31310415376 |
| 14 | 408815254832 |
| 15 | 5495451727376 |
| 16 | 75907303147652 |
| 17 | 1075685334980240 |
| 18 | 15618612118252960 |
| 19 | 232102241507321384 |
| 20 | 3526880759915999016 |
| 21 | 54755450619399484512 |
| 22 | 867928449982022915984 |