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 | -4 |
| 2 | 4 |
| 3 | 8 |
| 4 | -32 |
| 5 | 32 |
| 6 | 64 |
| 7 | -256 |
| 8 | 256 |
| 9 | 512 |
| 10 | -2048 |
| 11 | 2048 |
| 12 | 4096 |
| 13 | -16384 |
| 14 | 16384 |
| 15 | 32768 |
| 16 | -131072 |
| 17 | 131072 |
| 18 | 262144 |
| 19 | -1048576 |
| 20 | 1048576 |
| 21 | 2097152 |
| 22 | -8388608 |
| 23 | 8388608 |
| 24 | 16777216 |
| 25 | -67108864 |
| 26 | 67108864 |
| 27 | 134217728 |
| 28 | -536870912 |
| 29 | 536870912 |