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 | 2 |
| 1 | 1 |
| 2 | 3 |
| 3 | -1 |
| 4 | 7 |
| 5 | -9 |
| 6 | 23 |
| 7 | -41 |
| 8 | 87 |
| 9 | -169 |
| 10 | 343 |
| 11 | -681 |
| 12 | 1367 |
| 13 | -2729 |
| 14 | 5463 |
| 15 | -10921 |
| 16 | 21847 |
| 17 | -43689 |
| 18 | 87383 |
| 19 | -174761 |
| 20 | 349527 |
| 21 | -699049 |
| 22 | 1398103 |
| 23 | -2796201 |
| 24 | 5592407 |
| 25 | -11184809 |
| 26 | 22369623 |
| 27 | -44739241 |
| 28 | 89478487 |
| 29 | -178956969 |
| 30 | 357913943 |
| 31 | -715827881 |
| 32 | 1431655767 |
| 33 | -2863311529 |
| 34 | 5726623063 |