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 | -4 |
| 3 | -204 |
| 4 | -7776 |
| 5 | -358560 |
| 6 | -20839680 |
| 7 | -1516112640 |
| 8 | -135920332800 |
| 9 | -14772931891200 |
| 10 | -1917601910784000 |
| 11 | -293337284308992000 |
| 12 | -52263416690343936000 |
| 13 | -10734227287227924480000 |
| 14 | -2518467729187335045120000 |
| 15 | -669569466986357627289600000 |