I hope this is useful!

int main() {

int n;
scanf("%d", &n);
int a[2*n-1][2*n-1];
for (int i = 0; i<n; i++){
    for(int j = 0+i; j<2*n-1-i; j++){
        a[0+i][j] = n-i;
        a[j][0+i] = n-i;
        a[2*n-2-i][j] = n-i;
        a[j][2*n-2-i] = n-i;
    }
}
for(int i=0; i<2*n-1; i++){
    for(int j = 0; j<2*n-1; j++){
        printf("%d ", a[i][j]);
    }
    printf("\n");
}
return 0;

}