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 | 1 |
| 4 | -1 |
| 5 | 1 |
| 6 | 1 |
| 7 | -5 |
| 8 | -8 |
| 9 | 43 |
| 10 | -74 |
| 11 | -559 |
| 12 | 697 |
| 13 | -13232 |
| 14 | -30727 |
| 15 | 450991 |
| 16 | -5519014 |
| 17 | 8250311 |
| 18 | 59081053 |
| 19 | -2113948301 |
| 20 | 19352683736 |
| 21 | -113555728681 |
| 22 | -4421555920 |
| 23 | 10403170713454 |
| 24 | 4947541575776 |
| 25 | -1037548987977353 |
| 26 | 4668788227294924 |
| 27 | 20521746955820009 |