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 | 0 |
| 3 | 3 |
| 4 | 40 |
| 5 | 455 |
| 6 | 2016 |
| 7 | -177373 |
| 8 | -11564160 |
| 9 | -497664081 |
| 10 | -12796467200 |
| 11 | 536297904659 |
| 12 | 132025634657280 |
| 13 | 14907422733429239 |
| 14 | 1181852660381503488 |
| 15 | 34684559693802943875 |
| 16 | -11771644802057621110784 |
| 17 | -3553614228958108389522721 |
| 18 | -656899368126170250221715456 |