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 | 3 |
| 3 | -6 |
| 4 | 12 |
| 5 | -24 |
| 6 | 48 |
| 7 | -96 |
| 8 | 192 |
| 9 | -384 |
| 10 | 768 |
| 11 | -1536 |
| 12 | 3072 |
| 13 | -6144 |
| 14 | 12288 |
| 15 | -24576 |
| 16 | 49152 |
| 17 | -98304 |
| 18 | 196608 |
| 19 | -393216 |
| 20 | 786432 |
| 21 | -1572864 |
| 22 | 3145728 |
| 23 | -6291456 |
| 24 | 12582912 |
| 25 | -25165824 |
| 26 | 50331648 |
| 27 | -100663296 |
| 28 | 201326592 |
| 29 | -402653184 |
| 30 | 805306368 |
| 31 | -1610612736 |
| 32 | 3221225472 |