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 | 2 |
| 2 | 3 |
| 3 | 0 |
| 4 | 10 |
| 5 | -48 |
| 6 | 168 |
| 7 | 3456 |
| 8 | -29376 |
| 9 | -178560 |
| 10 | 0 |
| 11 | 2995200 |
| 12 | 0 |
| 13 | -45158400 |
| 14 | 1045094400 |
| 15 | -14636482560 |
| 16 | -122918584320 |
| 17 | -370845941760 |
| 18 | 12983695441920 |
| 19 | -1545691830681600 |
| 20 | -62521904633610240 |
| 21 | 785989658251100160 |
| 22 | -2445553599452282880 |