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) |
|---|---|
| 1 | 1 |
| 2 | -1 |
| 3 | -1 |
| 4 | 3 |
| 5 | 3 |
| 6 | -21 |
| 7 | 27 |
| 8 | 27 |
| 9 | -117 |
| 10 | 27 |
| 11 | 459 |
| 12 | -837 |
| 13 | -405 |
| 14 | 3483 |
| 15 | -2997 |
| 16 | -9477 |
| 17 | 25515 |
| 18 | -1701 |
| 19 | -91125 |
| 20 | 130491 |
| 21 | 165483 |
| 22 | -732645 |
| 23 | 422091 |
| 24 | 2136699 |
| 25 | -4546773 |
| 26 | -1712421 |
| 27 | 19597707 |
| 28 | -21237957 |
| 29 | -43597845 |
| 30 | 140635035 |
| 31 | -32890293 |
| 32 | -483552261 |
| 33 | 804188331 |