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 | -255 |
| 3 | -6560 |
| 4 | -65535 |
| 5 | -390624 |
| 6 | -1679615 |
| 7 | -5764800 |
| 8 | -16777215 |
| 9 | -43046720 |
| 10 | -99999999 |
| 11 | -214358880 |
| 12 | -429981695 |
| 13 | -815730720 |
| 14 | -1475789055 |
| 15 | -2562890624 |
| 16 | -4294967295 |
| 17 | -6975757440 |
| 18 | -11019960575 |
| 19 | -16983563040 |
| 20 | -25599999999 |
| 21 | -37822859360 |
| 22 | -54875873535 |