C Program to Print 0-10-101-0101 Binary Number Pattern

/* Program to print 0-10-101-0101 */
#include<stdio.h>

/* Main function */
int main()
{
    int i, j, n, a;
    printf("Enter number of lines of pattern: ");
    scanf("%d", &n);
    a = 0;
    for(i=1;i<=n;i++)
    {
        for(j=1;j<=i;j++)
        {
            printf("%d", a%2);
            a++;
        }
        printf("\n");
    }

    return 0;
}

output 

Enter number of lines of pattern: 11
0
10
101
0101
01010
101010
1010101
01010101
010101010
1010101010
10101010101