#include<stdio.h>
#include<conio.h>
int main() {

int n, i,j,p,s,p1;
s = 0;
p1 = 1;
printf("please enter your integer:");
scanf_s("%d", &n);



for (i = 0; i <= n - 1;i++) {

        for (j = i + 1;j <= n; j++)

        {
            p = i*j;

        }
    }




printf("%d", s);
    _getch();
    return 0;
}

#include<stdio.h>
#include<conio.h>
#include<math.h>        //inclue math.h for pow()
int main() {

int n, i,j,p,s,p1;
s = 0;
p1 = 1;
printf("please enter your integer:");
scanf("%d", &n);    //you can simply use scanf() here
s=p1;           //you forgot this


for (i = 1; i <= n - 1;i++) {

      s+=pow ((i*(i+1)),i);   // you dont need 2 for loops


    }

printf("%d", s);
    _getch();
    return 0;
}

#include <stdio.h>

int main(void)
{
    int n;
    int sum = 0;

    printf("Please enter the number of terms to sum: ");
    scanf("%d", &n);

    sum += 1;                       // First term

    /* Start loop with second term */
    for (int i = 2; i < n+1; i++) {
        int base = (i * (i + 1));
        int term = 1;

        for (int j = 0; j < i; j++) {
            term *= base;
        }
        sum += term;
    }
    printf("The sum of the first %d terms of the series is: %dn", n, sum);

    return 0;
}

Please enter the number of terms to sum: 2
The sum of the first 2 terms of the series is: 37

Please enter the number of terms to sum: 3
The sum of the first 3 terms of the series is: 1765

Please enter the number of terms to sum: 4
The sum of the first 4 terms of the series is: 161765

1 + (1*2)^1 + (2*3)^2 + (3*4)^3 + ... + ((n-1)*n)^(n-1)

int main(void)
{
    int n;
    unsigned long long sum = 0;

    printf("Please enter the number of terms to sum: ");
    scanf("%d", &n);

    /* Start loop with second term */
    for (int i = 1; i < n+1; i++) {
        unsigned long long base = ((i - 1) * i);
        unsigned long long term = 1;

        for (int j = 0; j < i-1; j++) {
            term *= base;
        }
        sum += term;
    }
    printf("The sum of the first %d terms of the series is: %llun", n, sum);

    return 0;
}

Please enter the number of terms to sum: 2
The sum of the first 2 terms of the series is: 3

Please enter the number of terms to sum: 3
The sum of the first 3 terms of the series is: 39

Please enter the number of terms to sum: 4
The sum of the first 4 terms of the series is: 1767

Please enter the number of terms to sum: 5
The sum of the first 5 terms of the series is: 161767