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) |
|---|---|
| 3 | 1 |
| 4 | 6 |
| 5 | 5 |
| 6 | -15 |
| 7 | 49 |
| 8 | -196 |
| 9 | 944 |
| 10 | -5340 |
| 11 | 34716 |
| 12 | -254760 |
| 13 | 2078856 |
| 14 | -18620784 |
| 15 | 180973584 |
| 16 | -1887504768 |
| 17 | 20887922304 |
| 18 | -242111586816 |
| 19 | 2889841121280 |
| 20 | -34586897978880 |
| 21 | 393722260047360 |
| 22 | -3659128846433280 |
| 23 | 5687630494110720 |
| 24 | 1137542166526464000 |
| 25 | -49644151627682304000 |