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 | -2 |
| 2 | 8 |
| 3 | -16 |
| 4 | 64 |
| 5 | -128 |
| 6 | 512 |
| 7 | -1024 |
| 8 | 4096 |
| 9 | -8192 |
| 10 | 32768 |
| 11 | -65536 |
| 12 | 262144 |
| 13 | -524288 |
| 14 | 2097152 |
| 15 | -4194304 |
| 16 | 16777216 |
| 17 | -33554432 |
| 18 | 134217728 |
| 19 | -268435456 |
| 20 | 1073741824 |
| 21 | -2147483648 |
| 22 | 8589934592 |
| 23 | -17179869184 |
| 24 | 68719476736 |
| 25 | -137438953472 |