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 | 1 |
| 3 | -7 |
| 4 | -11 |
| 5 | -151 |
| 6 | -419 |
| 7 | -1807 |
| 8 | -5291 |
| 9 | -381031 |
| 10 | -9125939 |
| 11 | -139879807 |
| 12 | -1217973371 |
| 13 | 7055720489 |
| 14 | 657464911741 |
| 15 | 20268419534993 |
| 16 | 455079458957749 |
| 17 | 7487596915540409 |
| 18 | 62151133224856621 |
| 19 | -943454812059725407 |
| 20 | -32387452121872219931 |
| 21 | 1120264679544729734729 |