import java.util.*;
class Main{
public static void main(String ...a){
int i,j,k=1;
Scanner sc= new Scanner(System.in);
System.out.print("Enter number of rows: ");
int n= sc.nextInt();
for(i = 1; i <= n; i++) {
for(j = 1;j <= i; j++)
System.out.print(" "+k++);
System.out.println("");
}
}
}
Output
Enter number of rows: 5
1
2 3
4 5 6
7 8 9 10
11 12 13 14 15