在系列1、8、54、384…中找到第N个术语

给定数字N。任务是编写一个程序来查找以下系列中的第N个术语：

1, 8, 54, 384...

例子：

Input : 3
Output : 54
For N = 3
Nth term = ( 3*3) * 3!
         = 54

Input : 2 
Output : 8

通过仔细观察，以上系列中的第N个术语可以概括为：

Nth term = ( N*N ) * ( N! )

下面是上述方法的实现：

C++

// CPP program to find N-th term of the series:
// 1, 8, 54, 384...
#include 
using namespace std;
 
// calculate factorial of N
int fact(int N)
{
    int i, product = 1;
    for (i = 1; i <= N; i++)
        product = product * i;
    return product;
}
 
// calculate Nth term of series
int nthTerm(int N)
{
    return (N * N) * fact(N);
}
 
// Driver Function
int main()
{
    int N = 4;
 
    cout << nthTerm(N);
 
    return 0;
}

Java

// Java program to find N-th term of the series:
// 1, 8, 54, 384...
 
import java.io.*;
 
// Main class for main method
class GFG {
    public static int fact(int N)
    {
        int i, product = 1;
        // Calculate factorial of N
        for (i = 1; i <= N; i++)
            product = product * i;
        return product;
    }
    public static int nthTerm(int N)
    {
        // By using above formula
        return (N * N) * fact(N);
    }
 
    public static void main(String[] args)
    {
        int N = 4; // 4th term is 384
 
        System.out.println(nthTerm(N));
    }
}

Python 3

# Python 3 program to find
# N-th term of the series:
# 1, 8, 54, 384...
 
# calculate factorial of N
def fact(N):
     
    product = 1
    for i in range(1, N + 1):
        product = product * i
    return product
 
# calculate Nth term of series
def nthTerm(N):
    return (N * N) * fact(N)
 
# Driver Code
if __name__ =="__main__":
    N = 4
    print(nthTerm(N))
 
# This code is contributed
# by ChitraNayal

C#

// C# program to find N-th
// term of the series:
// 1, 8, 54, 384...
using System;
 
class GFG
{
public static int fact(int N)
{
    int i, product = 1;
     
    // Calculate factorial of N
    for (i = 1; i <= N; i++)
        product = product * i;
    return product;
}
 
public static int nthTerm(int N)
{
    // By using above formula
    return (N * N) * fact(N);
}
 
// Driver Code
public static void Main(String[] args)
{
    int N = 4; // 4th term is 384
 
    Console.WriteLine(nthTerm(N));
}
}
 
// This code is contributed
// by Kirti_Mangal

Javascript

 
// JavaScript program to find N-th term of the series:
// 1, 8, 54, 384...
 
// calculate factorial of N
function fact( N)
{
    let i, product = 1;
    for (i = 1; i <= N; i++)
        product = product * i;
    return product;
}
 
// calculate Nth term of series
function nthTerm( N)
{
    return (N * N) * fact(N);
}
 
// Driver Function
 
    let N = 4;
    document.write(nthTerm(N));
     
// This code contributed by Rajput-Ji
 

输出：

384

时间复杂度： O(N)