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 | 6 |
| 4 | 0 |
| 5 | 60 |
| 6 | 2880 |
| 7 | 1680 |
| 8 | 201600 |
| 9 | 8074080 |
| 10 | 19958400 |
| 11 | 1824197760 |
| 12 | 69854400000 |
| 13 | 436929292800 |
| 14 | 36099561738240 |
| 15 | 1392369634656000 |
| 16 | 17026966410854400 |
| 17 | 1344523178718720000 |
| 18 | 54023115000830976000 |
| 19 | 1095484919871908966400 |
| 20 | 84994409643640713216000 |
| 21 | 3650011125774294048768000 |
| 22 | 109122812080533877712486400 |