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 | 0 |
| 2 | -1 |
| 3 | -6 |
| 4 | -19 |
| 5 | 20 |
| 6 | 899 |
| 7 | 7966 |
| 8 | 27705 |
| 9 | -366552 |
| 10 | -8374201 |
| 11 | -80690302 |
| 12 | 9794597 |
| 13 | 16015845820 |
| 14 | 317370642315 |
| 15 | 2554368906150 |
| 16 | -37571987331343 |
| 17 | -1784464543440304 |
| 18 | -31315944840101233 |
| 19 | -80221319702865398 |
| 20 | 12685422355781995485 |
| 21 | 422083364962616527716 |