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 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 3 |
| 4 | -28 |
| 5 | -150 |
| 6 | 2154 |
| 7 | 26040 |
| 8 | -322512 |
| 9 | -7872984 |
| 10 | 77570280 |
| 11 | 3752301960 |
| 12 | -22068935736 |
| 13 | -2542757920560 |
| 14 | 1422846762960 |
| 15 | 2302464947491800 |
| 16 | 14860063644794880 |
| 17 | -2653728770258072640 |
| 18 | -41790782141846648640 |
| 19 | 3739260018343338345600 |