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 | 0 |
| 2 | 4 |
| 3 | 120 |
| 4 | 33600 |
| 5 | 18471600 |
| 6 | 18386121600 |
| 7 | 30231607606200 |
| 8 | 76388992266787200 |
| 9 | 281063897503929540000 |
| 10 | 1444102677105174358272000 |
| 11 | 10020068498645397815029407000 |
| 12 | 91355440119583548608158042584000 |
| 13 | 1069762020017605579789451640683370000 |