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 | -1 |
| 4 | 1 |
| 5 | -3 |
| 6 | 17 |
| 7 | -85 |
| 8 | 385 |
| 9 | -1767 |
| 10 | 8929 |
| 11 | -50633 |
| 12 | 312705 |
| 13 | -2036267 |
| 14 | 13794417 |
| 15 | -97295069 |
| 16 | 717808897 |
| 17 | -5549714767 |
| 18 | 44868094145 |
| 19 | -377741383697 |
| 20 | 3298933836033 |
| 21 | -29813463964115 |
| 22 | 278462029910993 |
| 23 | -2685972391332837 |
| 24 | 26733375327601281 |
| 25 | -274247228584531767 |