Multiply a Hermite series by x.
Multiply the Hermite series c by x, where x is the independent variable.
| Parameters : | c : array_like 
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| Returns : | out : ndarray 
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Notes
The multiplication uses the recursion relationship for Hermite polynomials in the form

xP_i(x) = (P_{i + 1}(x) + iP_{i - 1}(x)))
Examples
>>> from numpy.polynomial.hermite_e import hermemulx
>>> hermemulx([1, 2, 3])
array([ 2.,  7.,  2.,  3.])