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 | -3 |
| 4 | 6 |
| 5 | -12 |
| 6 | 25 |
| 7 | -48 |
| 8 | 98 |
| 9 | -195 |
| 10 | 390 |
| 11 | -780 |
| 12 | 1561 |
| 13 | -3120 |
| 14 | 6242 |
| 15 | -12483 |
| 16 | 24966 |
| 17 | -49932 |
| 18 | 99865 |
| 19 | -199728 |
| 20 | 399458 |
| 21 | -798915 |
| 22 | 1597830 |
| 23 | -3195660 |
| 24 | 6391321 |
| 25 | -12782640 |
| 26 | 25565282 |
| 27 | -51130563 |
| 28 | 102261126 |
| 29 | -204522252 |
| 30 | 409044505 |
| 31 | -818089008 |
| 32 | 1636178018 |
| 33 | -3272356035 |
| 34 | 6544712070 |