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 | -3 |
| 3 | 14 |
| 4 | -85 |
| 5 | 504 |
| 6 | -4424 |
| 7 | 6796 |
| 8 | -878157 |
| 9 | -25703710 |
| 10 | -1270518018 |
| 11 | -65772588300 |
| 12 | -3848787714746 |
| 13 | -248212765567326 |
| 14 | -17520121174143210 |
| 15 | -1343050785659060872 |
| 16 | -111112550557260635229 |
| 17 | -9867409274482580015370 |
| 18 | -936234289413196544207234 |
| 19 | -94522404087905722536648780 |