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 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 12 |
| 5 | 96 |
| 6 | 240 |
| 7 | 4320 |
| 8 | 20160 |
| 9 | 241920 |
| 10 | 1451520 |
| 11 | 36288000 |
| 12 | 159667200 |
| 13 | 5748019200 |
| 14 | 37362124800 |
| 15 | 697426329600 |
| 16 | 10461394944000 |
| 17 | 334764638208000 |
| 18 | 2134124568576000 |
| 19 | 115242726703104000 |
| 20 | 973160803270656000 |
| 21 | 29194824098119680000 |
| 22 | 510909421717094400000 |