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 | -2 |
| 2 | -8 |
| 3 | -20 |
| 4 | -44 |
| 5 | -92 |
| 6 | -188 |
| 7 | -380 |
| 8 | -764 |
| 9 | -1532 |
| 10 | -3068 |
| 11 | -6140 |
| 12 | -12284 |
| 13 | -24572 |
| 14 | -49148 |
| 15 | -98300 |
| 16 | -196604 |
| 17 | -393212 |
| 18 | -786428 |
| 19 | -1572860 |
| 20 | -3145724 |
| 21 | -6291452 |
| 22 | -12582908 |
| 23 | -25165820 |
| 24 | -50331644 |
| 25 | -100663292 |
| 26 | -201326588 |
| 27 | -402653180 |
| 28 | -805306364 |
| 29 | -1610612732 |
| 30 | -3221225468 |