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) |
|---|---|
| 1 | 1 |
| 2 | -2 |
| 3 | -4 |
| 4 | 0 |
| 5 | -16 |
| 6 | 32 |
| 7 | -64 |
| 8 | 0 |
| 9 | 0 |
| 10 | 512 |
| 11 | -1024 |
| 12 | 0 |
| 13 | -4096 |
| 14 | 8192 |
| 15 | 16384 |
| 16 | 0 |
| 17 | -65536 |
| 18 | 0 |
| 19 | -262144 |
| 20 | 0 |
| 21 | 1048576 |
| 22 | 2097152 |
| 23 | -4194304 |
| 24 | 0 |
| 25 | 0 |
| 26 | 33554432 |
| 27 | 0 |
| 28 | 0 |
| 29 | -268435456 |
| 30 | -536870912 |
| 31 | -1073741824 |
| 32 | 0 |
| 33 | 4294967296 |
| 34 | 8589934592 |
| 35 | 17179869184 |
| 36 | 0 |
| 37 | -68719476736 |
| 38 | 137438953472 |
| 39 | 274877906944 |
| 40 | 0 |
| 41 | -1099511627776 |