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) |
|---|---|
| 1 | 1 |
| 2 | -1 |
| 3 | 1 |
| 4 | 3 |
| 5 | -39 |
| 6 | 257 |
| 7 | -909 |
| 8 | -6389 |
| 9 | 183715 |
| 10 | -2326009 |
| 11 | 15050003 |
| 12 | 140089725 |
| 13 | -6804608381 |
| 14 | 130909360315 |
| 15 | -1286161585477 |
| 16 | -12952744700713 |
| 17 | 970148927462835 |
| 18 | -25588194678272039 |
| 19 | 347909302401071797 |