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) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | -4 |
| 4 | -8 |
| 5 | -32 |
| 6 | -32 |
| 7 | -128 |
| 8 | -256 |
| 9 | -512 |
| 10 | -512 |
| 11 | -2048 |
| 12 | -4096 |
| 13 | -12288 |
| 14 | -16384 |
| 15 | -16384 |
| 16 | -32768 |
| 17 | -131072 |
| 18 | -262144 |
| 19 | -786432 |
| 20 | -1572864 |
| 21 | -2097152 |
| 22 | -2097152 |
| 23 | -8388608 |
| 24 | -16777216 |
| 25 | -33554432 |
| 26 | -33554432 |
| 27 | -67108864 |
| 28 | -134217728 |
| 29 | -536870912 |
| 30 | -1610612736 |
| 31 | -4294967296 |