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 | 0 |
| 4 | -4 |
| 5 | 0 |
| 6 | -16 |
| 7 | -32 |
| 8 | -28 |
| 9 | -288 |
| 10 | -400 |
| 11 | -1024 |
| 12 | -5268 |
| 13 | -5920 |
| 14 | -32160 |
| 15 | -82720 |
| 16 | -163020 |
| 17 | -737568 |
| 18 | -1482784 |
| 19 | -4644992 |
| 20 | -15095436 |
| 21 | -33307648 |
| 22 | -117747376 |
| 23 | -312435552 |
| 24 | -842726356 |
| 25 | -2747491616 |
| 26 | -7020371952 |
| 27 | -21348043296 |