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 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | -3 |
| 4 | 7 |
| 5 | -13 |
| 6 | 23 |
| 7 | -41 |
| 8 | 79 |
| 9 | -161 |
| 10 | 335 |
| 11 | -689 |
| 12 | 1391 |
| 13 | -2769 |
| 14 | 5487 |
| 15 | -10897 |
| 16 | 21743 |
| 17 | -43537 |
| 18 | 87279 |
| 19 | -174865 |
| 20 | 349935 |
| 21 | -699665 |
| 22 | 1398511 |
| 23 | -2795793 |
| 24 | 5590767 |
| 25 | -11182353 |
| 26 | 22367983 |
| 27 | -44740881 |
| 28 | 89485039 |
| 29 | -178966801 |
| 30 | 357920495 |
| 31 | -715821329 |
| 32 | 1431629551 |
| 33 | -2863272209 |
| 34 | 5726596847 |