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 | -5 |
| 2 | 5 |
| 3 | 30 |
| 4 | 180 |
| 5 | 1410 |
| 6 | 14790 |
| 7 | 203880 |
| 8 | 3559560 |
| 9 | 75659760 |
| 10 | 1893764160 |
| 11 | 54430097760 |
| 12 | 1763357958000 |
| 13 | 63501756552720 |
| 14 | 2514747808468080 |
| 15 | 108572621062573440 |
| 16 | 5074353268651935360 |
| 17 | 255201626973301102080 |
| 18 | 13740802156877800538880 |
| 19 | 788580746923723472839680 |