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Numeric evaluation of exp(x^2) in a sum TypeError

Define simple function of one variable with sum:

sage: r, i = var('r i')
sage: h(r) = sum(exp(i), i, -r, r)
sage: n(h(1))

OK, now change the argument of exponent to i^2:

sage: h(r) = sum(exp(i^2), i, -r, r)
sage: n(h(1))
TypeError                                 Traceback (most recent call last)
<ipython-input-128-85150c4c79b2> in <module>()
----> 1 n(h(Integer(1)))

/usr/lib/sagemath/local/lib/python2.7/site-packages/sage/misc/functional.pyc in numerical_approx(x, prec, digits)
   1395             prec = int((digits+1) * LOG_TEN_TWO_PLUS_EPSILON) + 1
   1396     try:
-> 1397         return x._numerical_approx(prec)
   1398     except AttributeError:
   1399         from sage.rings.complex_double import is_ComplexDoubleElement

/usr/lib/sagemath/local/lib/python2.7/site-packages/sage/symbolic/ in sage.symbolic.expression.Expression._numerical_approx (sage/symbolic/expression.cpp:22617)()

TypeError: cannot evaluate symbolic expression numerically

Why is that and what am I doing wrong?