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 | 1 |
| 2 | -2 |
| 3 | -3 |
| 4 | -10 |
| 5 | -19 |
| 6 | -42 |
| 7 | -83 |
| 8 | -170 |
| 9 | -339 |
| 10 | -682 |
| 11 | -1363 |
| 12 | -2730 |
| 13 | -5459 |
| 14 | -10922 |
| 15 | -21843 |
| 16 | -43690 |
| 17 | -87379 |
| 18 | -174762 |
| 19 | -349523 |
| 20 | -699050 |
| 21 | -1398099 |
| 22 | -2796202 |
| 23 | -5592403 |
| 24 | -11184810 |
| 25 | -22369619 |
| 26 | -44739242 |
| 27 | -89478483 |
| 28 | -178956970 |
| 29 | -357913939 |
| 30 | -715827882 |
| 31 | -1431655763 |