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 | 2 |
| 2 | -6 |
| 3 | -12 |
| 4 | 30 |
| 5 | 60 |
| 6 | -140 |
| 7 | -280 |
| 8 | 630 |
| 9 | 1260 |
| 10 | -2772 |
| 11 | -5544 |
| 12 | 12012 |
| 13 | 24024 |
| 14 | -51480 |
| 15 | -102960 |
| 16 | 218790 |
| 17 | 437580 |
| 18 | -923780 |
| 19 | -1847560 |
| 20 | 3879876 |
| 21 | 7759752 |
| 22 | -16224936 |
| 23 | -32449872 |
| 24 | 67603900 |
| 25 | 135207800 |
| 26 | -280816200 |
| 27 | -561632400 |
| 28 | 1163381400 |
| 29 | 2326762800 |
| 30 | -4808643120 |
| 31 | -9617286240 |
| 32 | 19835652870 |