`CauchyMatrix[x, y]` is the matrix with entry (i, j) equal to `1/(x_i + y_j)`.
CauchyMatrix[x, y]
CauchyMatrix[x]
CauchyMatrix[cmat]
CauchyMatrix[{1, 2, 3}, {1, 5, 6}]
→ CauchyMatrix[StructuredArray`StructuredData[{3, 3}, {{1, 2, 3}, {1, 5, 6}}]]Normal[CauchyMatrix[{1, 2, 3}, {1, 5}]]
→ {{1/2, 1/6}, {1/3, 1/7}, {1/4, 1/8}}CauchyMatrix[{1, 2, 3}, TargetStructure -> "Dense"]
→ {{1/2, 1/3, 1/4}, {1/3, 1/4, 1/5}, {1/4, 1/5, 1/6}}CauchyMatrix[{{1/2, 1/3}, {1/3, 1/4}}]
→ CauchyMatrix[StructuredArray`StructuredData[{2, 2}, {{2, 3}, {0, 1}}]]