Matlab Resistance (size mismatch error)

I need to use matlab to find a convolution in the range 0 <= n <= 20.

x [n] = δ [n] + δ [n-2] and h [n] = 2 * (3 ^ n) u [n]

I tried to do this and I was met with "X is not the same length as Y" when trying to build it and tried to fix it. Can anyone inform me if this is correct?

 n = [0:20];
 x =[1 0 1];
 h= 2*3.^n;
 y = conv(x,h);
 ysize = size(y,2)
 z = [0:(ysize-1)];
 ysize = size (y,2);
 p = stem(z ,y ,'r' ,'filled');
 set (p, 'LineWidth', 2, 'MarkerSize', 4);
 title ('y[n] = x[n] * h[n]');
 xlabel ('n');
 ylabel ('y[n]');