Последовательность.. с циклом do .. while

int f6()
{
cout <<" iterativnue  ziklisheskie   struktury   do .... loop "<<endl;
_getch();
 
double x;
double eps;
 
double r1;
double r2;
double sum;
double a;
double ch;
double delta;
 int n;
n=0;
cout<<"------------------------------------------------"<<endl;
    cout<<"zadayte   x =0.7       x  = ";
    cin>> x;
 
cout<<"zadayte   eps=0.00005     eps = ";
    cin>> eps;
cout<<"---------------------------------------------------------------------------"<<endl;
cout<<"|     n  |      r1   |      r2   |       a   |      delta    |   sum       |"<<endl;
cout<<"---------------------------------------------------------------------------"<<endl;
 
/////////////////f5_1();
sum=1;
r1=x*x;
r2=2;
a=r1/r2;
////delta=abs(a-eps);
n=n+1;
while(a>eps)
{
sum=sum+a;
 
cout<<"|"<<setw(3)<<n<<setw(15)<<r1<<setw(10)<<r2<<setw(15)<<a<<setw(15)<<delta<<setw(15)<<sum<<setw(2)<<"|"<<endl;
cout<<"|--------------------------------------------------------------------------|"<<endl;
 
n=n+1;
r1=r1*(x*x);
 
r2=r2*((2*n)*(2*n-1));
 
a=r1/r2;
 
delta=abs(eps-a);
 
}
_getch();
 
return 0;
}

int i = 1;
double x = 0.3;
double eps = 0.001;
while ( (fabs(powl(x, i)/(4*i*i - 1))) > eps)
{
 cout << "i = " << i <<", a_i = " << (powl(x, i)/(4*i*i-1)) << endl; 
}