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 | -2 |
| 5 | 25 |
| 6 | -75 |
| 7 | 1099 |
| 8 | -4340 |
| 9 | 79064 |
| 10 | -382060 |
| 11 | 8550916 |
| 12 | -48306984 |
| 13 | 1303568760 |
| 14 | -8346754416 |
| 15 | 266955481584 |
| 16 | -1894529909376 |
| 17 | 70785236377728 |
| 18 | -547468189825536 |
| 19 | 23610353987137536 |
| 20 | -196402650598402560 |
| 21 | 9679304091074250240 |
| 22 | -85687212859582878720 |
| 23 | 4785340778000524477440 |