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 | 1 |
| 2 | 0 |
| 3 | 6 |
| 4 | 0 |
| 5 | 170 |
| 6 | -120 |
| 7 | 12446 |
| 8 | -35336 |
| 9 | 1832400 |
| 10 | -12172320 |
| 11 | 469680552 |
| 12 | -5524990416 |
| 13 | 189586178184 |
| 14 | -3321122831208 |
| 15 | 111608536026360 |
| 16 | -2599887499382400 |
| 17 | 90253048158627072 |
| 18 | -2595580675897337856 |
| 19 | 95720854442948910720 |
| 20 | -3237436187047116892800 |