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 | -3 |
| 2 | 5 |
| 3 | -9 |
| 4 | 18 |
| 5 | -36 |
| 6 | 72 |
| 7 | -144 |
| 8 | 288 |
| 9 | -576 |
| 10 | 1152 |
| 11 | -2304 |
| 12 | 4608 |
| 13 | -9216 |
| 14 | 18432 |
| 15 | -36864 |
| 16 | 73728 |
| 17 | -147456 |
| 18 | 294912 |
| 19 | -589824 |
| 20 | 1179648 |
| 21 | -2359296 |
| 22 | 4718592 |
| 23 | -9437184 |
| 24 | 18874368 |
| 25 | -37748736 |
| 26 | 75497472 |
| 27 | -150994944 |
| 28 | 301989888 |
| 29 | -603979776 |
| 30 | 1207959552 |
| 31 | -2415919104 |
| 32 | 4831838208 |