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 | 0 |
| 2 | -1 |
| 3 | 3 |
| 4 | -8 |
| 5 | 22 |
| 6 | -64 |
| 7 | 196 |
| 8 | -625 |
| 9 | 2055 |
| 10 | -6917 |
| 11 | 23713 |
| 12 | -82499 |
| 13 | 290511 |
| 14 | -1033411 |
| 15 | 3707851 |
| 16 | -13402696 |
| 17 | 48760366 |
| 18 | -178405156 |
| 19 | 656043856 |
| 20 | -2423307046 |
| 21 | 8987427466 |
| 22 | -33453694486 |
| 23 | 124936258126 |
| 24 | -467995871776 |
| 25 | 1757900019100 |
| 26 | -6619846420552 |
| 27 | 24987199492704 |
| 28 | -94520750408708 |