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 | -2 |
| 3 | -4 |
| 4 | 0 |
| 5 | 16 |
| 6 | 0 |
| 7 | 0 |
| 8 | -128 |
| 9 | 256 |
| 10 | -512 |
| 11 | 2048 |
| 12 | -6144 |
| 13 | 16384 |
| 14 | -49152 |
| 15 | 147456 |
| 16 | -425984 |
| 17 | 1245184 |
| 18 | -3670016 |
| 19 | 10747904 |
| 20 | -31457280 |
| 21 | 92274688 |
| 22 | -270532608 |
| 23 | 792723456 |
| 24 | -2323644416 |
| 25 | 6811549696 |
| 26 | -19964887040 |
| 27 | 58518929408 |
| 28 | -171530256384 |
| 29 | 502779609088 |
| 30 | -1473710653440 |
| 31 | 4319663357952 |