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) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | -1 |
| 4 | 4 |
| 5 | -11 |
| 6 | -4 |
| 7 | -547 |
| 8 | 7680 |
| 9 | -7751 |
| 10 | 81744 |
| 11 | -3258663 |
| 12 | -9474816 |
| 13 | -390445563 |
| 14 | 233029824 |
| 15 | -964154427 |
| 16 | 4193551958016 |
| 17 | -18431412645519 |
| 18 | 71090090006784 |
| 19 | -6436900596281679 |
| 20 | 17349989459410944 |
| 21 | 834261829219880829 |
| 22 | -241960391975347200 |
| 23 | -1149793471388581053219 |