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 | -4 |
| 3 | 16 |
| 4 | -74 |
| 5 | 386 |
| 6 | -2180 |
| 7 | 12974 |
| 8 | -80087 |
| 9 | 507887 |
| 10 | -3288564 |
| 11 | 21649068 |
| 12 | -144458484 |
| 13 | 974838450 |
| 14 | -6641303895 |
| 15 | 45615642021 |
| 16 | -315530731215 |
| 17 | 2196107692119 |
| 18 | -15368596890978 |
| 19 | 108073850591598 |
| 20 | -763293549312084 |
| 21 | 5412015893523096 |
| 22 | -38508964818580799 |