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 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 0 |
| 5 | 0 |
| 6 | -5 |
| 7 | 5 |
| 8 | -56 |
| 9 | 224 |
| 10 | -1441 |
| 11 | 9029 |
| 12 | -64592 |
| 13 | 497068 |
| 14 | -4153357 |
| 15 | 37288173 |
| 16 | -358469008 |
| 17 | 3672613632 |
| 18 | -39954165153 |
| 19 | 459970973037 |
| 20 | -5587015067704 |
| 21 | 71405586701516 |
| 22 | -957909748415229 |
| 23 | 13458304798985221 |
| 24 | -197627582943979080 |