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 | 0 |
| 1 | 1 |
| 2 | -1 |
| 3 | 4 |
| 4 | -33 |
| 5 | 456 |
| 6 | -9460 |
| 7 | 274800 |
| 8 | -10643745 |
| 9 | 530052880 |
| 10 | -32995478376 |
| 11 | 2510382661920 |
| 12 | -229195817258100 |
| 13 | 24730000147369440 |
| 14 | -3113066087894608560 |
| 15 | 452168671458789789504 |
| 16 | -75059305956331837485345 |
| 17 | 14121026957032156557396000 |
| 18 | -2988687741694684876495689040 |