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 | -1 |
| 2 | 0 |
| 3 | 2 |
| 4 | -7 |
| 5 | 21 |
| 6 | -63 |
| 7 | 195 |
| 8 | -624 |
| 9 | 2054 |
| 10 | -6916 |
| 11 | 23712 |
| 12 | -82498 |
| 13 | 290510 |
| 14 | -1033410 |
| 15 | 3707850 |
| 16 | -13402695 |
| 17 | 48760365 |
| 18 | -178405155 |
| 19 | 656043855 |
| 20 | -2423307045 |
| 21 | 8987427465 |
| 22 | -33453694485 |
| 23 | 124936258125 |
| 24 | -467995871775 |
| 25 | 1757900019099 |
| 26 | -6619846420551 |