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 | 4 |
| 2 | 36 |
| 3 | 1 |
| 4 | 3600 |
| 5 | 1 |
| 6 | 211680 |
| 7 | 1 |
| 8 | 10886400 |
| 9 | 1 |
| 10 | 526901760 |
| 11 | 1 |
| 12 | 16999766784000 |
| 13 | 1 |
| 14 | 1120863744000 |
| 15 | 1 |
| 16 | 181400588328960000 |
| 17 | 1 |
| 18 | 97072790126247936000 |
| 19 | 1 |
| 20 | 16860010916664115200000 |
| 21 | 1 |
| 22 | 324325300906011525120000 |
| 23 | 1 |