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 | 1 |
| 3 | 0 |
| 4 | -2 |
| 5 | 12 |
| 6 | -16 |
| 7 | 144 |
| 8 | 368 |
| 9 | 4768 |
| 10 | 39488 |
| 11 | 412288 |
| 12 | 4577280 |
| 13 | 55671808 |
| 14 | 731390976 |
| 15 | 10335518720 |
| 16 | 156303439872 |
| 17 | 2518984822784 |
| 18 | 43099089166336 |
| 19 | 780268880543744 |
| 20 | 14902336357040128 |
| 21 | 299452809649520640 |
| 22 | 6315501510334480384 |
| 23 | 139485953831272710144 |
| 24 | 3219718099932104622080 |