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 | 2 |
| 3 | -2 |
| 4 | -20 |
| 5 | 54 |
| 6 | 894 |
| 7 | 38746 |
| 8 | -559964 |
| 9 | -30609658 |
| 10 | -31739522 |
| 11 | 35082324322 |
| 12 | 1906861094012 |
| 13 | -35137055357704 |
| 14 | -9062074392580500 |
| 15 | -356229387136444332 |
| 16 | 29618152958504386488 |
| 17 | 5528234516989447402962 |
| 18 | 199584070046140925795142 |
| 19 | -46670714204947255394726486 |