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 | -4 |
| 2 | 5 |
| 3 | -15 |
| 4 | 31 |
| 5 | -72 |
| 6 | 160 |
| 7 | -361 |
| 8 | 810 |
| 9 | -1821 |
| 10 | 4091 |
| 11 | -9193 |
| 12 | 20656 |
| 13 | -46414 |
| 14 | 104291 |
| 15 | -234340 |
| 16 | 526557 |
| 17 | -1183163 |
| 18 | 2658543 |
| 19 | -5973692 |
| 20 | 13422764 |
| 21 | -30160677 |
| 22 | 67770426 |
| 23 | -152278765 |
| 24 | 342167279 |
| 25 | -768842897 |
| 26 | 1727574308 |
| 27 | -3881824234 |
| 28 | 8722379879 |
| 29 | -19599009684 |
| 30 | 44038575013 |