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 | -6 |
| 2 | -13 |
| 3 | -27 |
| 4 | -50 |
| 5 | -106 |
| 6 | -208 |
| 7 | -412 |
| 8 | -840 |
| 9 | -1656 |
| 10 | -3328 |
| 11 | -6672 |
| 12 | -13280 |
| 13 | -26656 |
| 14 | -53248 |
| 15 | -106432 |
| 16 | -213120 |
| 17 | -425856 |
| 18 | -851968 |
| 19 | -1704192 |
| 20 | -3407360 |
| 21 | -6816256 |
| 22 | -13631488 |
| 23 | -27261952 |
| 24 | -54528000 |
| 25 | -109049856 |
| 26 | -218103808 |
| 27 | -436211712 |
| 28 | -872407040 |
| 29 | -1744838656 |