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 | 0 |
| 2 | -1 |
| 3 | 0 |
| 4 | 12 |
| 5 | 1 |
| 6 | 0 |
| 7 | -120 |
| 8 | -420 |
| 9 | -1 |
| 10 | 0 |
| 11 | 896 |
| 12 | 36400 |
| 13 | 10248 |
| 14 | 1 |
| 15 | 0 |
| 16 | -5760 |
| 17 | -2170560 |
| 18 | -4858560 |
| 19 | -196920 |
| 20 | -1 |
| 21 | 0 |
| 22 | 33792 |
| 23 | 102960000 |
| 24 | 1127738304 |
| 25 | 461126160 |
| 26 | 3247860 |
| 27 | 1 |
| 28 | 0 |
| 29 | -186368 |
| 30 | -4083183104 |
| 31 | -187282263168 |
| 32 | -340884800256 |
| 33 | -35248293080 |
| 34 | -48361404 |
| 35 | -1 |
| 36 | 0 |
| 37 | 983040 |
| 38 | 141360128000 |
| 39 | 25081621813248 |
| 40 | 153279541958400 |
| 41 | 76526954183680 |
| 42 | 2290777550880 |
| 43 | 669616080 |
| 44 | 1 |