View Compilation Error

0_0_30283011_28451.cpp: In function 'int main()':
0_0_30283011_28451.cpp:5:2: error: expected ',' or ';' before 'a'
  a=0
  ^
0_0_30283011_28451.cpp:9:18: error: 'arr' was not declared in this scope
   printf("%d\n", arr[n]);           
                  ^
0_0_30283011_28451.cpp:11:3: error: 'a' was not declared in this scope
   a = (n*n*n - 4) * 8;     
   ^