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 | -9 |
| 2 | 56 |
| 3 | -328 |
| 4 | 1912 |
| 5 | -11144 |
| 6 | 64952 |
| 7 | -378568 |
| 8 | 2206456 |
| 9 | -12860168 |
| 10 | 74954552 |
| 11 | -436867144 |
| 12 | 2546248312 |
| 13 | -14840622728 |
| 14 | 86497488056 |
| 15 | -504144305608 |
| 16 | 2938368345592 |
| 17 | -17126065767944 |
| 18 | 99818026262072 |
| 19 | -581782091804488 |
| 20 | 3390874524564856 |
| 21 | -19763465055584648 |