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) |
|---|---|
| 1 | 0 |
| 2 | 3 |
| 3 | -6 |
| 4 | -30 |
| 5 | 360 |
| 6 | 504 |
| 7 | -44016 |
| 8 | 204048 |
| 9 | 8261760 |
| 10 | -128422272 |
| 11 | -1816480512 |
| 12 | 76562054400 |
| 13 | 124207469568 |
| 14 | -51042832542720 |
| 15 | 580686719698944 |
| 16 | 36632422458820608 |
| 17 | -1141184282933624832 |
| 18 | -23612862502431719424 |
| 19 | 1881307594631033978880 |
| 20 | 253019693533000826880 |