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 | 0 |
| 2 | 2 |
| 3 | -2 |
| 4 | 6 |
| 5 | -10 |
| 6 | 22 |
| 7 | -42 |
| 8 | 86 |
| 9 | -170 |
| 10 | 342 |
| 11 | -682 |
| 12 | 1366 |
| 13 | -2730 |
| 14 | 5462 |
| 15 | -10922 |
| 16 | 21846 |
| 17 | -43690 |
| 18 | 87382 |
| 19 | -174762 |
| 20 | 349526 |
| 21 | -699050 |
| 22 | 1398102 |
| 23 | -2796202 |
| 24 | 5592406 |
| 25 | -11184810 |
| 26 | 22369622 |
| 27 | -44739242 |
| 28 | 89478486 |
| 29 | -178956970 |
| 30 | 357913942 |
| 31 | -715827882 |
| 32 | 1431655766 |
| 33 | -2863311530 |
| 34 | 5726623062 |