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 | 2 |
| 4 | 0 |
| 5 | -16 |
| 6 | 24 |
| 7 | 104 |
| 8 | -256 |
| 9 | -1600 |
| 10 | 5632 |
| 11 | 29952 |
| 12 | -156032 |
| 13 | -644736 |
| 14 | 4761600 |
| 15 | 18383616 |
| 16 | -178225152 |
| 17 | -645554176 |
| 18 | 8081772544 |
| 19 | 25645936640 |
| 20 | -422364381184 |
| 21 | -1160636121088 |
| 22 | 25184814366720 |
| 23 | 60217271582720 |
| 24 | -1713906141986816 |