Visual Studio Code – How does memory alloc work in C? // What's wrong w my code?

New to programming, im doing a problem where I’m supposed to print a square pattern of decreasing numbers like 5 would give:

5 5 5 5 5 5 5 5 5 
5 4 4 4 4 4 4 4 5 
5 4 3 3 3 3 3 4 5 
5 4 3 2 2 2 3 4 5 
5 4 3 2 1 2 3 4 5 
5 4 3 2 2 2 3 4 5 
5 4 3 3 3 3 3 4 5 
5 4 4 4 4 4 4 4 5 
5 5 5 5 5 5 5 5 5

i thought of using arrays and repeatedly subtracting from the array and printing it to solve this;

#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>

int main() 
{

    int n;
    scanf("%d", &n);
    // Complete the code to print the pattern.
    int *arr;
    int k=1;
    arr = calloc(2*n-1, sizeof(char));
    
    for (int i = 0; i < 2*n-1; i++) {
        *(arr + i) = n;
    }
    do {
        for (int i = 0; i < 2*n-1; i++) {
            printf("%d ", arr[i]);
            
        }
        printf("n");
        for (int i = k; i < 2*n-1-k; i++) {
            arr[i] = arr[i] - 1;
        }
        k++;
        
    } while ( k <= n);
    
    k=n-1;
    
    for (int j = 1; j < n; j++) {
        
        for (int i = k; i <2*n-1-k; i++) {
            arr[i]++;
        }
        k--;
        
        for (int i = 0; i < 2*n-1; i++) {
            printf("%d ", arr[i]);
        }
        printf("n");
    }
    
    return 0;
}

this works in Visual studio code, but not on the compiler on the site, and not on another online compiler i tested it on. I’m assuming i messed up on the calloc part. What’s the problem here?