C code fragment [closed]

Question

In the following C program fragment, j, k, n and TwoLog_n are integer variables, and A is an array of integers. The variable n is initialized to an integer $\ge3$, and TwoLog_n is initialized to the value of $2\lceil\log{2n}\rceil$

for (k=3; k <= n; k++)
  A[k] = 0;
for (k=2; k <= TwoLog_n; k++)
  for (j=k+1; j <= n; j++)
    A[j] = A[j] || (j%k);
for (j=3; j <= n; j++)
  if (!A[j]) printf(”%d ”,j);

Can anyone tell me what this piece of code fragment basically does??

Answer 1

It appears that it attempts to print all integer values between $3$ and $n$ (inclusive) for which each is completely divisible by all integers in the range $[2,2 \cdot \lceil log_2(n)\rceil]$ less than itself. A finer point is that it preserves the first non zero remainder value discovered in the corresponding array element instead of overriding it with subsequent non zero values. This may simply be an unintended result of coding "shorthand."