Printing out each time 2 more elements of an array - c

Question

How can I print out each line two more elements of an array...?
I can't get it done.
I have this short code, but this part is missing...
#include <stdio.h>
#include <stdlib.h>
char *toChar(int numbers[]);
int main(){
// FILE *fp;
int num;
printf("Number of rows: ");
scanf("%d", &num);
int val[num], value=num;
for(int i=0; i<num; i++){
val[i]=value;
value+=value;
printf("%d ", val[i]);
...
printf("\n");
}
}
return 0;
}
I would like to achieve this... for input = 4.
4 8
12 16 20 24
28 32 36 40 44 48
52 56 60 64 68 72 76 80
And for input 3, expected output is:
3 6
9 12 15 18
21 24 27 30 33 36
Note that the printed value should increase by the same amount as there should be rows (num).

Answer 1

I would make a list of all you need:
You need num rows
You need the number of columns to increase by 2 every row
You need the printed value to increase by num for each output
With that list, make two loops.
One that iterates over the rows
One that iterates over the columns:
#include <stdio.h>
int main() {
printf("Number of rows: ");
int num;
if (scanf("%d", &num) != 1) return 1;
// row starts at 0 and ends at num-1
// columns start with 2 and increases by 2 for every row
for (int row = 0, columns = 2, value = num; row < num; ++row, columns += 2) {
// and value increases by `num` every time it's been printed:
for (int c = 0; c < columns; ++c, value += num) {
printf("%d ", value);
}
putchar('\n');
}
}
Demo

Answer 2

Decided to take a stab at this using java. I feel like recursion here was a bit easier than trying to wrap my head around two for loops.
class Main {
public static void main(String[] args) {
printTwoMore(0, 1, 1, 4);
}
public static void printTwoMore(int prevTimesToPrint, int multiple, int currentRow, int maxRow) {
if (currentRow > maxRow) {
return;
}
int timesToPrint = 2 + prevTimesToPrint;
for (int i = 0; i < timesToPrint; i++) {
System.out.print(4 * multiple + " ");
multiple++;
}
System.out.println("");
currentRow++;
printTwoMore(timesToPrint, multiple, currentRow, maxRow);
}
}