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 | 20 |
| 2 | 110 |
| 3 | 340 |
| 4 | -1995 |
| 5 | 53904 |
| 6 | -1534600 |
| 7 | 49159600 |
| 8 | -1758057650 |
| 9 | 69662897000 |
| 10 | -3037327435860 |
| 11 | 144787947993000 |
| 12 | -7502235351828450 |
| 13 | 420296374337607600 |
| 14 | -25335189019626256200 |
| 15 | 1636008982452733508400 |
| 16 | -112721505676611504401025 |
| 17 | 8256863266451569604835900 |