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 | -2 |
| 2 | 5 |
| 3 | -29 |
| 4 | 265 |
| 5 | -3191 |
| 6 | 47321 |
| 7 | -832040 |
| 8 | 16908641 |
| 9 | -389806471 |
| 10 | 10049731549 |
| 11 | -286482047279 |
| 12 | 8946795882025 |
| 13 | -303762892305614 |
| 14 | 11140078609864049 |
| 15 | -438857301101610929 |
| 16 | 18482410314337295233 |
| 17 | -828657053219851847135 |
| 18 | 39406519321199703822581 |
| 19 | -1981132660316876165976260 |