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) |
|---|---|
| 1 | 1 |
| 2 | -2 |
| 3 | 11 |
| 4 | -28 |
| 5 | 85 |
| 6 | -238 |
| 7 | 735 |
| 8 | -2216 |
| 9 | 6585 |
| 10 | -19610 |
| 11 | 59059 |
| 12 | -177428 |
| 13 | 531453 |
| 14 | -1593606 |
| 15 | 4783175 |
| 16 | -14351152 |
| 17 | 43046737 |
| 18 | -129134082 |
| 19 | 387420507 |
| 20 | -1162281100 |
| 21 | 3486785925 |
| 22 | -10460294174 |
| 23 | 31381059631 |
| 24 | -94143360856 |
| 25 | 282429536825 |
| 26 | -847288078026 |
| 27 | 2541865841523 |
| 28 | -7625599078020 |
| 29 | 22876792454989 |