Auto-correlation of a sequence x without using xcorr(x)

It is the correlation of a signal with a delayed copy of itself as a function of delay.

Enter x
[1 1 2 3 4]
Enter the lower limit:
-1
Enter the upper limit:
3
x(n) is:
1 1 2 3 4

z(n) is:
4 3 2 1 1

y(n) is:
4 7 13 21 31 21 13 7 4