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 | 1 |
| 2 | 0 |
| 3 | 0 |
| 4 | 24 |
| 5 | 1080 |
| 6 | 52440 |
| 7 | 3281880 |
| 8 | 277953144 |
| 9 | 32418855000 |
| 10 | 5239070305080 |
| 11 | 1173944480658840 |
| 12 | 363936227764858584 |
| 13 | 155521768202208047640 |
| 14 | 91218870039317505477720 |
| 15 | 73113879800794757415243480 |
| 16 | 79743817918540500914682249144 |
| 17 | 117883366412734188786535902826200 |
| 18 | 235329353612778837110901775412557560 |