C二级辅导-等差数列 （C语言代码）

#include<stdio.h>
int sums(int n)
{
	int sum;
	sum=(3*n+1)*n/2;
	return sum;	
} 
int main(void)
{
	int n,sum;
	scanf("%d",&n);
	printf("%d",sums(n));
	return 0;
}

int main(){
    int i,n,sum; //n个整数 
    scanf("%d",&n);
    for(i=0;i<n;i++){
        sum=2+2*i+i*3;
    }
    printf("%d",sum);
    return 0;
}

#include<stdio.h>
int main()
{
    int n,i,m=0,sum=0;
    scanf("%d",&n);
    for(i=1;i<=n;i++)
    {
        m=2+3*(i-1);
        sum+=m;
    }
    printf("%d",sum);
	return 0;
}

#include<stdio.h>


int main()
{
	int x,c;
	scanf("%d",&x);
	c=x*(3*x+1)/2;
	printf("%d",c);
	return 0;
}

#include<stdio.h>
int main()
{
	int a;
	scanf("%d",&a);
	printf("%d",(3*a*a+a)/2 );
	return 0;
}

int main()
{
	int n = 0;
	int sum = 2;
	int j = 2;
	scanf("%d", &n);
	for (int i = 1; i < n; i++)
	{
		j = j + 3;
		sum = j + sum;
	}
	printf("%d", sum);

	
	
	
}

难住我的是编程吗，是数学

#include<stdio.h>
int main()
{
   int *q,n,s;
   q=&n;
   scanf("%d",q);
   s=2*(*q)+(*q*(*q-1)/2)*3;
   printf("%d",s);
   return 0;

}