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 | -6 |
| 3 | 36 |
| 4 | -272 |
| 5 | 2304 |
| 6 | -20880 |
| 7 | 198080 |
| 8 | -1942080 |
| 9 | 19521792 |
| 10 | -200101376 |
| 11 | 2083538688 |
| 12 | -21976624128 |
| 13 | 234321952768 |
| 14 | -2521446660096 |
| 15 | 27347192389632 |
| 16 | -298643542716416 |
| 17 | 3280990949720064 |
| 18 | -36238161907974144 |
| 19 | 402146115064233984 |
| 20 | -4481721683926056960 |