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 | 6 |
| 3 | 12 |
| 4 | 180 |
| 5 | 504 |
| 6 | 12960 |
| 7 | 45360 |
| 8 | 1710720 |
| 9 | 7076160 |
| 10 | 359251200 |
| 11 | 1698278400 |
| 12 | 109930867200 |
| 13 | 580811212800 |
| 14 | 46170964224000 |
| 15 | 268334780313600 |
| 16 | 25486372251648000 |
| 17 | 161000868188160000 |
| 18 | 17891433320656896000 |
| 19 | 121716656350248960000 |
| 20 | 15565546988971499520000 |
| 21 | 113196490405731532800000 |