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 | 2 |
| 3 | -2 |
| 4 | -6 |
| 5 | 9 |
| 6 | -3 |
| 7 | 24 |
| 8 | -44 |
| 9 | 24 |
| 10 | -4 |
| 11 | -120 |
| 12 | 250 |
| 13 | -175 |
| 14 | 50 |
| 15 | -5 |
| 16 | 720 |
| 17 | -1644 |
| 18 | 1350 |
| 19 | -510 |
| 20 | 90 |
| 21 | -6 |
| 22 | -5040 |
| 23 | 12348 |
| 24 | -11368 |
| 25 | 5145 |
| 26 | -1225 |
| 27 | 147 |
| 28 | -7 |
| 29 | 40320 |
| 30 | -104544 |
| 31 | 105056 |
| 32 | -54152 |
| 33 | 15680 |
| 34 | -2576 |
| 35 | 224 |
| 36 | -8 |
| 37 | -362880 |
| 38 | 986256 |
| 39 | -1063116 |
| 40 | 605556 |
| 41 | -202041 |
| 42 | 40824 |
| 43 | -4914 |
| 44 | 324 |
| 45 | -9 |
| 46 | 3628800 |
| 47 | -10265760 |
| 48 | 11727000 |
| 49 | -7236800 |