Find, with proof, all integers $n$ such that there is a solution in nonnegative real numbers $(x,y,z)$ to the system of equations
\[2x^2+3y^2+6z^2=n\text{ and }3x+4y+5z=23.\]
To find all integers \( n \) such that there is a solution in nonnegative real numbers \((x, y, z)\) to the system of equations:
\[ 2x^2 + 3y^2 + 6z^2 = n \]
\[ 3x + 4y + 5z = 23 \]

we will proceed as follows:

1. **Express \( z \) in terms of \( x \) and \( y \) from the second equation:**
   \[ 3x + 4y + 5z = 23 \]
   \[ 5z = 23 - 3x - 4y \]
   \[ z = \frac{23 - 3x - 4y}{5} \]

2. **Substitute \( z \) into the first equation:**
   \[ 2x^2 + 3y^2 + 6\left(\frac{23 - 3x - 4y}{5}\right)^2 = n \]
   \[ 2x^2 + 3y^2 + 6\left(\frac{529 - 138x - 184y + 9x^2 + 24xy + 16y^2}{25}\right) = n \]
   \[ 2x^2 + 3y^2 + \frac{6}{25}(529 - 138x - 184y + 9x^2 + 24xy + 16y^2) = n \]
   \[ 2x^2 + 3y^2 + \frac{3174 - 828x - 1104y + 54x^2 + 144xy + 96y^2}{25} = n \]
   \[ 2x^2 + 3y^2 + \frac{3174}{25} - \frac{828x}{25} - \frac{1104y}{25} + \frac{54x^2}{25} + \frac{144xy}{25} + \frac{96y^2}{25} = n \]
   \[ 2x^2 + 3y^2 + \frac{3174}{25} - \frac{828x}{25} - \frac{1104y}{25} + \frac{54x^2}{25} + \frac{144xy}{25} + \frac{96y^2}{25} = n \]

3. **Combine like terms:**
   \[ 2x^2 + 3y^2 + \frac{54x^2}{25} + \frac{96y^2}{25} + \frac{144xy}{25} - \frac{828x}{25} - \frac{1104y}{25} + \frac{3174}{25} = n \]
   \[ 2x^2 + 3y^2 + 2.16x^2 + 3.84y^2 + 5.76xy - 33.12x - 44.16y + 126.96 = n \]
   \[ 4.16x^2 + 6.84y^2 + 5.76xy - 33.12x - 44.16y + 126.96 = n \]

4. **Determine the range of \( n \):**
   Since \( x, y, z \) are nonnegative real numbers, we need to find the minimum and maximum values of \( n \).

   - **Minimum value of \( n \):**
     When \( x = 0, y = 0, z = \frac{23}{5} \):
     \[ 2(0)^2 + 3(0)^2 + 6\left(\frac{23}{5}\right)^2 = n \]
     \[ 6 \cdot \frac{529}{25} = n \]
     \[ n = \frac{3174}{25} = 126.96 \]

   - **Maximum value of \( n \):**
     When \( x = 0, y = 0, z = 0 \):
     \[ 2(0)^2 + 3(0)^2 + 6(0)^2 = n \]
     \[ n = 0 \]

5. **Conclusion:**
   Since \( n \) must be an integer, the only possible value for \( n \) is 127.

The final answer is \( \boxed{ n = 127 } \)