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 | 6 |
| 3 | -12 |
| 4 | -84 |
| 5 | 1200 |
| 6 | 3120 |
| 7 | -249312 |
| 8 | 920928 |
| 9 | 86274816 |
| 10 | -1232035584 |
| 11 | -40970012160 |
| 12 | 1391730516480 |
| 13 | 20983074318336 |
| 14 | -1798371774277632 |
| 15 | -1850681724997632 |
| 16 | 2713439169345073152 |
| 17 | -40045819902128750592 |
| 18 | -4625352042615223025664 |
| 19 | 171173842584165886328832 |
| 20 | 8223835353617664214695936 |