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 | 3 |
| 2 | 3 |
| 3 | 15 |
| 4 | 3 |
| 5 | 87 |
| 6 | -69 |
| 7 | 591 |
| 8 | -1005 |
| 9 | 4551 |
| 10 | -10581 |
| 11 | 37887 |
| 12 | -101373 |
| 13 | 328695 |
| 14 | -936933 |
| 15 | 2909103 |
| 16 | -8530701 |
| 17 | 25985319 |
| 18 | -77169525 |
| 19 | 233081439 |
| 20 | -696098589 |
| 21 | 2094587223 |
| 22 | -6271178757 |
| 23 | 18838702095 |
| 24 | -56465774637 |
| 25 | 169497987207 |
| 26 | -508292635029 |