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 | -3 |
| 2 | 6 |
| 3 | -15 |
| 4 | 33 |
| 5 | -78 |
| 6 | 177 |
| 7 | -411 |
| 8 | 942 |
| 9 | -2175 |
| 10 | 5001 |
| 11 | -11526 |
| 12 | 26529 |
| 13 | -61107 |
| 14 | 140694 |
| 15 | -324015 |
| 16 | 746097 |
| 17 | -1718142 |
| 18 | 3956433 |
| 19 | -9110859 |
| 20 | 20980158 |
| 21 | -48312735 |
| 22 | 111253209 |
| 23 | -256191414 |
| 24 | 589951041 |
| 25 | -1358525283 |
| 26 | 3128378406 |
| 27 | -7203954255 |
| 28 | 16589089473 |