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 | 6 |
| 2 | -36 |
| 3 | 360 |
| 4 | -4320 |
| 5 | 57024 |
| 6 | -798336 |
| 7 | 11632896 |
| 8 | -174493440 |
| 9 | 2675566080 |
| 10 | -41738830848 |
| 11 | 660232415232 |
| 12 | -10563718643712 |
| 13 | 170644685783040 |
| 14 | -2779070597038080 |
| 15 | 45576757791424512 |
| 16 | -752016503558504448 |
| 17 | 12474626706088132608 |
| 18 | -207910445101468876800 |
| 19 | 3479764291698268569600 |