How to create pattern of 1-10 in a triangle?

CODE

How to create pattern of 1-10 in a triangle?

int main()

{

    int i,j,a=1;

    for(i=1;i<=4;i++)

    {

        for(j=1;j<=i;j++)

        {

            printf("%d ",a);

            a++;

        }

        printf("\n");

    }

}

Output:

1

2  3

4  5  6

7  8  9  10