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 | 0 |
| 2 | 0 |
| 3 | -4 |
| 4 | -12 |
| 5 | -60 |
| 6 | -220 |
| 7 | -936 |
| 8 | -4092 |
| 9 | -17840 |
| 10 | -80868 |
| 11 | -356172 |
| 12 | -1640872 |
| 13 | -7433604 |
| 14 | -34541160 |
| 15 | -159080304 |
| 16 | -743832276 |
| 17 | -3469487112 |
| 18 | -16321682424 |
| 19 | -76796957940 |
| 20 | -363235185312 |
| 21 | -1720415299660 |
| 22 | -8176521038556 |