I think what Eugen Podsypalnikov saying is true...
If you want to make it user define series just add one variable in it.
#include <stdio.h>
int main()
{
int i, j, n;
printf("Enter range : ");
scanf("%d",&n);
for (i = 1; i <= n; i++) {
for (j = 1; j <= i; j++) {
prinf("%d ", i);
}
printf("\n");
}
return 0;
}