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 | -3 |
| 3 | 12 |
| 4 | -66 |
| 5 | 480 |
| 6 | -4368 |
| 7 | 47712 |
| 8 | -608016 |
| 9 | 8855040 |
| 10 | -145083648 |
| 11 | 2641216512 |
| 12 | -52891055616 |
| 13 | 1155444326400 |
| 14 | -27344999497728 |
| 15 | 696933753434112 |
| 16 | -19031293222127616 |
| 17 | 554336947975618560 |
| 18 | -17155693983744196608 |