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 | -1 |
| 4 | -10 |
| 5 | -6 |
| 6 | 294 |
| 7 | 1350 |
| 8 | -14624 |
| 9 | -197568 |
| 10 | 703800 |
| 11 | 34790040 |
| 12 | 100585968 |
| 13 | -7259053296 |
| 14 | -85604489712 |
| 15 | 1588693382640 |
| 16 | 46549054391040 |
| 17 | -216669088277760 |
| 18 | -24865626969568512 |
| 19 | -159153249738896640 |
| 20 | 13379663931502199040 |