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 | 5 |
| 3 | -13 |
| 4 | 39 |
| 5 | -113 |
| 6 | 331 |
| 7 | -965 |
| 8 | 2819 |
| 9 | -8229 |
| 10 | 24027 |
| 11 | -70149 |
| 12 | 204811 |
| 13 | -597973 |
| 14 | 1745867 |
| 15 | -5097301 |
| 16 | 14882283 |
| 17 | -43450901 |
| 18 | 126860971 |
| 19 | -370388309 |
| 20 | 1081400363 |
| 21 | -3157299285 |
| 22 | 9218175915 |
| 23 | -26913751125 |
| 24 | 78578452651 |
| 25 | -229420759381 |
| 26 | 669825926315 |
| 27 | -1955650276693 |
| 28 | 5709793924779 |