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 | 4 |
| 3 | -6 |
| 4 | -16 |
| 5 | 310 |
| 6 | -3144 |
| 7 | 28826 |
| 8 | -260000 |
| 9 | 2345094 |
| 10 | -20901880 |
| 11 | 176084986 |
| 12 | -1216168944 |
| 13 | 1862029910 |
| 14 | 186232275544 |
| 15 | -6005924996070 |
| 16 | 144514137334976 |
| 17 | -3177768345524954 |
| 18 | 67577079942366120 |
| 19 | -1420754665075404166 |
| 20 | 29799354626069718640 |