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 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 6218175600 |
| 5 | 15281788354560 |
| 6 | 9026867482214400 |
| 7 | 1989179450818560000 |
| 8 | 213006159759990870000 |
| 9 | 13144087517631410995200 |
| 10 | 525100718690287495741440 |
| 11 | 14756609779472604266496000 |
| 12 | 310160311536865273422120000 |