generate number

[h4ever]

New target:

I would like to generate number from sumerizing of the previous numbers like this:

// 1 2 3 4 5 6 7   8   9   10         11 12   13   14    15   16    17    18
// 2 4  7  11 16 23 30 38 47 57 68 80  93   107 122  138  150  168 

Can you help what do I need change?

Based on this thread:
http://www.cplusplus.com/forum/beginner/3212/

code of pet:

#include <iostream>
#include <conio.h>
using namespace std;

int fib(int n)
{
  if(1 == n || 2 == n)
  {
      return 1;
  }
  else
  {
      return fib(n-1) + fib(n-2);
  }

}

int main()
{
    for(int i=1; i<=15; i++)
    {
        cout << fib(i) << endl;
    }
	getch();
    return 0;
}

Is it posible to make function to this one, having ability to get the number i, when you know the Fibonacci number?

[MatthewRock]

You mean a function with output like this?

Please input Fibonacci number: 8
8 is 6. Fibonacci number

It certainly is possible, but you will have to create a new function :)

[Chervil]

Perhaps this might help - there's mountains of information on the Fibonacci numbers here, and your specific question is discussed, with a formula given, as well as an online demonstration.
http://www.maths.surrey.ac.uk/hosted-sites/R.Knott/Fibonacci/fibFormula.html#detectfib

[h4ever]

MatthewRock
I mean, when FN is 610, what is n? n is 15.
When I know that n is 15, so I can generate new FN: either lower or greater:
fib(15-1);fib(15+1); depending on what I need.

[h4ever]

Topic changed:

I would like to generate number from sumerizing of the previous numbers like this:

#include <iostream>
#include <conio.h>
using namespace std;
// 1 2 3 4 5 6 7   8   9   10         11 12   13   14    15   16    17    18
// 2 4  7  11 16 23 30 38 47 57 68 80  93   107 122  138  150  168
int sum(int i, int &r)
{
r = i+r;
return r;
}

int main()
{   
	int result=-1;
	int &r = result;
    for(int i=1; i<=30; i++)
    {
        cout << i << " : " << sum(i, r) << endl;
    }
	_getch();
    return 0;
}

I tried to initiate the number result as 0 (higher numbers) or -1 a smaller numbers (not ideal because at i=1 should be r=1 or higher. Any idea how to correct this to give this?
2 4 7 11 16 23 30 38 47 57 68 80 93 107 122 138 150 168
I tried to simplify as much as possible