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 | -84 |
| 5 | 64 |
| 6 | 320 |
| 7 | 1540 |
| 8 | -4296 |
| 9 | 22774 |
| 10 | -11504 |
| 11 | -5472 |
| 12 | 13752 |
| 13 | -18325 |
| 14 | -4808916 |
| 15 | 22766346 |
| 16 | 5005440 |
| 17 | 519618712 |
| 18 | -216839949 |
| 19 | -913585532 |
| 20 | 4352326994 |
| 21 | 15724880927 |
| 22 | 0 |
| 23 | -44298224496 |
| 24 | 783852776697 |
| 25 | -173267864064 |
| 26 | -601092343023697 |
| 27 | 26866456767483 |
| 28 | 39073758546015 |