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 | -15 |
| 3 | -143 |
| 4 | 1 |
| 5 | 12801 |
| 6 | 100401 |
| 7 | -555855 |
| 8 | -16006143 |
| 9 | -69903359 |
| 10 | 1371541105 |
| 11 | 20881151985 |
| 12 | 5878439425 |
| 13 | -2725373454335 |
| 14 | -25310084063055 |
| 15 | 145439041081137 |
| 16 | 4851621446905857 |
| 17 | 23952290336559105 |
| 18 | -470461357757965071 |
| 19 | -7793050905481342863 |
| 20 | -4149447893184517119 |