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 | 2 |
| 1 | -1 |
| 2 | -4 |
| 3 | -40 |
| 4 | -4960 |
| 5 | -147166720 |
| 6 | -299211527038566400 |
| 7 | -2703337074029927682081937523621232640 |