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) |
|---|---|
| 2 | 1 |
| 3 | 4 |
| 4 | 13 |
| 5 | 30 |
| 6 | -14 |
| 7 | -504 |
| 8 | 736 |
| 9 | 44640 |
| 10 | -104544 |
| 11 | -10644480 |
| 12 | 33246720 |
| 13 | 5425056000 |
| 14 | -20843695872 |
| 15 | -5185511654400 |
| 16 | 23457840537600 |
| 17 | 8506857655296000 |
| 18 | -44092609863966720 |
| 19 | -22430879475779174400 |
| 20 | 130748316971139072000 |