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 | 1 |
| 2 | 0 |
| 3 | 2 |
| 4 | 0 |
| 5 | 0 |
| 6 | 4 |
| 7 | -4 |
| 8 | 4 |
| 9 | 4 |
| 10 | -12 |
| 11 | 20 |
| 12 | -12 |
| 13 | -12 |
| 14 | 52 |
| 15 | -76 |
| 16 | 52 |
| 17 | 52 |
| 18 | -204 |
| 19 | 308 |
| 20 | -204 |
| 21 | -204 |
| 22 | 820 |
| 23 | -1228 |
| 24 | 820 |
| 25 | 820 |
| 26 | -3276 |
| 27 | 4916 |
| 28 | -3276 |
| 29 | -3276 |
| 30 | 13108 |
| 31 | -19660 |
| 32 | 13108 |
| 33 | 13108 |
| 34 | -52428 |
| 35 | 78644 |
| 36 | -52428 |
| 37 | -52428 |
| 38 | 209716 |
| 39 | -314572 |
| 40 | 209716 |
| 41 | 209716 |
| 42 | -838860 |
| 43 | 1258292 |
| 44 | -838860 |
| 45 | -838860 |
| 46 | 3355444 |
| 47 | -5033164 |
| 48 | 3355444 |