What is wrong with the logic of this code that sums bands of numbers?

Question

My algorithm needs to sum all the values between a and b, for example if I type a=3 e b=6 the program needs to speak 3 7 12 18 (3+4= 7/ 7+5=12 / 12+6=18) only he only makes the first two then starts to miss.

#include <stdio.h>  

int main ()  
{  

int a,b,i,n,x,c;  

  printf("Digite a: ");  
  scanf("%d", &a);  
  printf("Digite b: ");  
  scanf("%d", &b);  

  c=0;  
  for(i=1;i<=b;i++)  
  {  
    c=a;  
    a=c+(a+1);  

    printf("%d\n ",c);  

  }


    return 0;  
}

Answer 1

The code is a bit confusing and tries to do too many things. Just start the loop with the first data entered and end on the second. The end is correct, but you need to start with a.

#include <stdio.h>  

int main() {
    int a, b;
    printf("Digite a: ");
    scanf("%d", &a);
    printf("Digite b: ");
    scanf("%d", &b);
    int soma = 0;
    for (int i = a; i <= b; i++) {
        soma += i;
        printf("%d ", soma);
    }
}

Behold working in the ideone. And in the repl it.. Also put on the Github for future reference.

Answer 2

#include <stdio.h>

int main()
{
    int a, b, soma=0, i;

    printf("Digite a: ");
    scanf("%d", &a);
    printf("Digite b: ");
    scanf("%d", &b);

    for(i=0; i<=b; i++)
    {
        if(i >= a)
        {
            soma = soma + i;
        }
    }
    printf("%i\n", soma);
}