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 | 0 |
| 3 | 0 |
| 4 | -2 |
| 5 | -10 |
| 6 | -62 |
| 7 | -518 |
| 8 | -5042 |
| 9 | -55914 |
| 10 | -700982 |
| 11 | -9801022 |
| 12 | -151141850 |
| 13 | -2548546130 |
| 14 | -46648614014 |
| 15 | -921144036486 |
| 16 | -19518279101570 |
| 17 | -441740723440186 |
| 18 | -10635049333176902 |
| 19 | -271391755745104334 |
| 20 | -7317268150934309162 |
| 21 | -207850529950047641250 |