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 | -1 |
| 3 | -55 |
| 4 | 217 |
| 5 | -2441 |
| 6 | 41911 |
| 7 | -343519 |
| 8 | 10531025 |
| 9 | -123024817 |
| 10 | 2722259791 |
| 11 | -64395229031 |
| 12 | 1218005521129 |
| 13 | -36874422541945 |
| 14 | 785879799954887 |
| 15 | -25331247487596751 |
| 16 | 708096286059632161 |
| 17 | -21422225147712360929 |
| 18 | 741754828422824400415 |