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) |
|---|---|
| 4 | 1 |
| 5 | 5 |
| 6 | 30 |
| 7 | 210 |
| 8 | 1680 |
| 9 | 15120 |
| 10 | 151200 |
| 11 | 1663200 |
| 12 | 19958400 |
| 13 | 259459200 |
| 14 | 3632428800 |
| 15 | 54486432000 |
| 16 | 871782912000 |
| 17 | 14820309504000 |
| 18 | 266765571072000 |
| 19 | 5068545850368000 |
| 20 | 101370917007360000 |
| 21 | 2128789257154560000 |
| 22 | 46833363657400320000 |
| 23 | 1077167364120207360000 |