iztrans not giving correct result?

I wrote a program to first find out z transform X of input x and then secondly applied inverse z transform to X to get back original x but when i use the iztrans command , i do not get the original input as shown highlighted in attached phot. My code is as follow

 clc
 clear all
 close all
 syms z n
 x=n^2*heaviside(n)  % original input
 X=ztrans(x,z)       % z transform of input
 x1=iztrans(X,n)     % Application of inverse z transform to get back original input

Answer 1

[KALYAN ACHARJYA]

Check here

Answer 2

[Paul]

 syms z n

The fact that the default value for heaviside(0) = 1/2 doesn't matter here, but should be kept in mid in general.

 x=n^2*heaviside(n)  % original input

x = 

 X=ztrans(x,z)       % z transform of input

X = 

 x1=iztrans(X,n)     % Application of inverse z transform to get back original input

x1 = 

 expand(x1) % bearing in mind that the output of iztrans is only valid for n >= 0

ans =