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 | -1 |
| 2 | 3 |
| 3 | -7 |
| 4 | 16 |
| 5 | -36 |
| 6 | 80 |
| 7 | -176 |
| 8 | 384 |
| 9 | -832 |
| 10 | 1792 |
| 11 | -3840 |
| 12 | 8192 |
| 13 | -17408 |
| 14 | 36864 |
| 15 | -77824 |
| 16 | 163840 |
| 17 | -344064 |
| 18 | 720896 |
| 19 | -1507328 |
| 20 | 3145728 |
| 21 | -6553600 |
| 22 | 13631488 |
| 23 | -28311552 |
| 24 | 58720256 |
| 25 | -121634816 |
| 26 | 251658240 |
| 27 | -520093696 |
| 28 | 1073741824 |
| 29 | -2214592512 |
| 30 | 4563402752 |
| 31 | -9395240960 |
| 32 | 19327352832 |