HoldForm

The next line gives a sum of integers squared.

Sum[HoldForm[#^2] &[i], {i, 1, 9}]

1^2 + 2^2 + 3^2 + 4^2 + 5^2 + 6^2 + 7^2 + 8^2 + 9^2

We can use ReleaseHold to complete the calculation.

ReleaseHold[%]

285

Created by Mathematica  (May 16, 2004)