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 | -15 |
| 4 | 49 |
| 5 | 1365 |
| 6 | -7645 |
| 7 | -311311 |
| 8 | 2475473 |
| 9 | 132652377 |
| 10 | -1367593305 |
| 11 | -90881245455 |
| 12 | 1151541572401 |
| 13 | 91341008892445 |
| 14 | -1373222414339685 |
| 15 | -126594821384553375 |
| 16 | 2202549127844351265 |
| 17 | 231390624855674406705 |
| 18 | -4573116447815658471025 |
| 19 | -539278542630309415030735 |