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 | -3 |
| 2 | -11 |
| 3 | 15 |
| 4 | 599 |
| 5 | -395 |
| 6 | -3893 |
| 7 | 20855 |
| 8 | 1297199 |
| 9 | -1869111 |
| 10 | -315196855 |
| 11 | 255365275 |
| 12 | 304261665587 |
| 13 | -49453295827 |
| 14 | -1056627547637 |
| 15 | 12890470331775 |
| 16 | 26749039258693183 |
| 17 | -4351895477983343 |
| 18 | -2270808628615272191 |
| 19 | 1847319496652416355 |
| 20 | 3100305824682616298389 |