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 | -6 |
| 3 | 27 |
| 4 | -141 |
| 5 | 819 |
| 6 | -5022 |
| 7 | 31968 |
| 8 | -209202 |
| 9 | 1398420 |
| 10 | -9505854 |
| 11 | 65499759 |
| 12 | -456410943 |
| 13 | 3210397173 |
| 14 | -22763553876 |
| 15 | 162524220984 |
| 16 | -1167359075781 |
| 17 | 8429107868541 |
| 18 | -61148608627518 |
| 19 | 445450238075655 |
| 20 | -3257116365714831 |
| 21 | 23896262127268719 |
| 22 | -175854177039133998 |