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 | 0 |
| 4 | -1 |
| 5 | 0 |
| 6 | -1 |
| 7 | 1 |
| 8 | -8 |
| 9 | 54 |
| 10 | -530 |
| 11 | 6192 |
| 12 | -86581 |
| 13 | 1425517 |
| 14 | -27298232 |
| 15 | 601580873 |
| 16 | -15116315768 |
| 17 | 429614643061 |
| 18 | -13711655205089 |
| 19 | 488332318973593 |
| 20 | -19296579341940069 |
| 21 | 841693047573682615 |
| 22 | -40338071854059455414 |
| 23 | 2115074863808199160560 |
| 24 | -120866265222965259346028 |