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 | -1 |
| 2 | -3 |
| 3 | -5 |
| 4 | -175 |
| 5 | -441 |
| 6 | -4851 |
| 7 | -14157 |
| 8 | -2760615 |
| 9 | -8690825 |
| 10 | -112285459 |
| 11 | -370263621 |
| 12 | -19870814327 |
| 13 | -67607800225 |
| 14 | -931331941875 |
| 15 | -3241035157725 |
| 16 | -2913690606794775 |
| 17 | -10313859829588425 |
| 18 | -147068001273760875 |
| 19 | -527570807893408125 |
| 20 | -30451387031607516975 |