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) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 4 |
| 3 | -36 |
| 4 | -96 |
| 5 | 450 |
| 6 | 1080 |
| 7 | -3920 |
| 8 | -8960 |
| 9 | 28350 |
| 10 | 63000 |
| 11 | -182952 |
| 12 | -399168 |
| 13 | 1093092 |
| 14 | 2354352 |
| 15 | -6177600 |
| 16 | -13178880 |
| 17 | 33474870 |
| 18 | 70887960 |
| 19 | -175518200 |
| 20 | -369512000 |
| 21 | 896251356 |
| 22 | 1877859984 |
| 23 | -4478082336 |
| 24 | -9345563136 |
| 25 | 21971267500 |
| 26 | 45700236400 |
| 27 | -106148523600 |
| 28 | -220159900800 |