nces of coefficients ordered from lowest order term to
highest, i.e., [1,2,3] represents the series ``P_0 + 2*P_1 + 3*P_2``.

Parameters
----------
c1, c2 : array_like
    1-D arrays of Legendre series coefficients ordered from low to
    high.

Returns
-------
out : ndarray
    Array representing the Legendre series of their sum.

See Also
--------
legsub, legmulx, legmul, legdiv, legpow

Notes
-----
Unlike multiplication, division, etc., the sum of two Legendre series
is a Legendre series (without having to "reproject" the result onto
the basis set) so addition, just like that of "standard" polynomials,
is simply "component-wise."

Examples
--------
>>> from numpy.polynomial import legendre as L
>>> c1 = (1,2,3)
>>> c2 = (3,2,1)
>>> L.legadd(c1,c2)
array([4.,  4.,  4.])

)