This program will give you an idea of adding a series having
only odd numbers. Let a series
1+3+5+7+……..25. Now Define the first odd number by a variable and last
odd number by another variable. Then use a while loop for performing sum
operation. Here I used variable i as loop counter as well as putting each odd
number of the series on it. While loop will stop when i>lastODDnumber

//1+3+5+..............+n

#include <stdio.h>

main(){

int i,n1,n2,SUM=0;

printf("Insert the first
ODD number: ");

scanf("%d",&n1);

printf("Insert the last
ODD number: ");

scanf("%d",&n2);

i=n1; //initialize i by first
odd number

while(i<=n2){

SUM=i+SUM;

i=i+2;

}

printf("Total:
%d",SUM);

return 0;

}