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 | -2 |
| 2 | 2 |
| 3 | 0 |
| 4 | -2 |
| 5 | 0 |
| 6 | 4 |
| 7 | 0 |
| 8 | -10 |
| 9 | 0 |
| 10 | 28 |
| 11 | 0 |
| 12 | -84 |
| 13 | 0 |
| 14 | 264 |
| 15 | 0 |
| 16 | -858 |
| 17 | 0 |
| 18 | 2860 |
| 19 | 0 |
| 20 | -9724 |
| 21 | 0 |
| 22 | 33592 |
| 23 | 0 |
| 24 | -117572 |
| 25 | 0 |
| 26 | 416024 |
| 27 | 0 |
| 28 | -1485800 |
| 29 | 0 |
| 30 | 5348880 |
| 31 | 0 |
| 32 | -19389690 |
| 33 | 0 |
| 34 | 70715340 |
| 35 | 0 |
| 36 | -259289580 |
| 37 | 0 |
| 38 | 955277400 |
| 39 | 0 |
| 40 | -3534526380 |
| 41 | 0 |
| 42 | 13128240840 |
| 43 | 0 |
| 44 | -48932534040 |
| 45 | 0 |
| 46 | 182965127280 |
| 47 | 0 |
| 48 | -686119227300 |
| 49 | 0 |