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 | 1 |
| 2 | 2 |
| 3 | 3 |
| 4 | -16 |
| 5 | -255 |
| 6 | -1824 |
| 7 | 875 |
| 8 | 279040 |
| 9 | 5019777 |
| 10 | 34163200 |
| 11 | -822579021 |
| 12 | -35005820928 |
| 13 | -598199789759 |
| 14 | 1612679634944 |
| 15 | 456446015789595 |
| 16 | 15087057004396544 |
| 17 | 168732823928006145 |
| 18 | -8490541860738957312 |
| 19 | -560665092239473776157 |
| 20 | -14661549133472721797120 |