C++ :: Display Arithmetic Sequence After Adding All Numbers

This code is suppose to display arithmetic sequence after it has to add all the numbers together without a formula.

for example: the starting number is 5, common difference is 3, the term is 9

the sequence would display as: 5, 8, 11, 14, 17, 20, 23, 26, 29

the sum is: 153

with my code I've managed to get 8,11

To get the sum, I am restricted to using a "for" loop. For sequence, I am using a while. I am trouble developing the while loop to display the sequence and getting the sum for the for loop.

#include <iostream>
#include <cmath>
#include <stdlib.h>
using namespace std;
int main() {
double a, d, n,i,sum,j;

[Code] ....