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 | 2 |
| 4 | -15 |
| 5 | -46 |
| 6 | 880 |
| 7 | 5837 |
| 8 | -132783 |
| 9 | -2109238 |
| 10 | 35966256 |
| 11 | 1440196097 |
| 12 | -8909037720 |
| 13 | -1504006716551 |
| 14 | -16097564749643 |
| 15 | 2021100230840147 |
| 16 | 83130656159529937 |
| 17 | -2475528081920694566 |
| 18 | -331363460045748820376 |
| 19 | -3874344448291316066455 |
| 20 | 1255007424437046915956520 |