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 | 0 |
| 3 | -1 |
| 4 | 4 |
| 5 | -11 |
| 6 | 66 |
| 7 | -547 |
| 8 | 4880 |
| 9 | -27351 |
| 10 | 263310 |
| 11 | -3258663 |
| 12 | 39791016 |
| 13 | -390445563 |
| 14 | 5477278548 |
| 15 | -84140635815 |
| 16 | 1486404086016 |
| 17 | -18431412645519 |
| 18 | 322018685539542 |
| 19 | -6436900596281679 |
| 20 | 133183534639917240 |
| 21 | -2208721087854287811 |
| 22 | 49383164607876494604 |
| 23 | -1149793471388581053219 |