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 | 1 |
| 3 | 0 |
| 4 | -2 |
| 5 | 0 |
| 6 | 1 |
| 7 | 6 |
| 8 | 0 |
| 9 | -6 |
| 10 | 1 |
| 11 | -24 |
| 12 | 0 |
| 13 | 35 |
| 14 | -10 |
| 15 | -2 |
| 16 | 120 |
| 17 | 0 |
| 18 | -225 |
| 19 | 85 |
| 20 | 30 |
| 21 | -9 |
| 22 | -720 |
| 23 | 0 |
| 24 | 1624 |
| 25 | -735 |
| 26 | -350 |
| 27 | 189 |
| 28 | -9 |
| 29 | 5040 |
| 30 | 0 |
| 31 | -13132 |
| 32 | 6769 |
| 33 | 3920 |
| 34 | -2898 |
| 35 | 252 |
| 36 | 50 |
| 37 | -40320 |
| 38 | 0 |
| 39 | 118124 |
| 40 | -67284 |
| 41 | -44898 |
| 42 | 40824 |
| 43 | -4914 |
| 44 | -1800 |
| 45 | 267 |
| 46 | 362880 |
| 47 | 0 |
| 48 | -1172700 |
| 49 | 723680 |