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 | 4 |
| 1 | 5 |
| 2 | 3 |
| 3 | 7 |
| 4 | -1 |
| 5 | 15 |
| 6 | -17 |
| 7 | 47 |
| 8 | -81 |
| 9 | 175 |
| 10 | -337 |
| 11 | 687 |
| 12 | -1361 |
| 13 | 2735 |
| 14 | -5457 |
| 15 | 10927 |
| 16 | -21841 |
| 17 | 43695 |
| 18 | -87377 |
| 19 | 174767 |
| 20 | -349521 |
| 21 | 699055 |
| 22 | -1398097 |
| 23 | 2796207 |
| 24 | -5592401 |
| 25 | 11184815 |
| 26 | -22369617 |
| 27 | 44739247 |
| 28 | -89478481 |
| 29 | 178956975 |
| 30 | -357913937 |
| 31 | 715827887 |
| 32 | -1431655761 |
| 33 | 2863311535 |