Рекурсия

#include <iostream>
#include <cstdlib>
 
using namespace std;
 
int b;
 
int prod(int n)
{
    if (n <= 2 )
        return b;
    else
        return (b + n) * prod((n%2) + 1);
}
 
int main()
{
    int n;
    int p;
    cout << "Input integral b: ";
    cin >> b;
    cout << "Input integer number >= 0: ";
    cin >> n;
    p = prod(n);
    cout << "Product of b * (b + 2) * (b + 4) * ... * (b + 2n) ";
    cout << "For a = " << b << " and n = " << n << " :p = " << p << endl;
    system("PAUSE");
    return EXIT_SUCCESS;
}

int prod(int n)
{
    if (n <= 0)
        return b;
    else
        return (b + 2 * n) * prod(n - 1);
}

#include <iostream>
using namespace std;
 
long long prod(int n, int b)
{
    if (n == 0)
        return b;
    else
        return (b + 2 * n) * prod(n - 1, b);
}
 
int main()
{
    int n, b;
    long long p;
    cout << "Input integral b: ";
    cin >> b;
    cout << "Input integer number >= 0: ";
    cin >> n;
    p = prod(n, b);
    cout << "Product of b(b + 2)(b + 4)...(b + 2n) ";
    cout << "for b = " << b << " and n = " << n << ": p = " << p << endl;
    system("pause");
    return 0;
}