程序以找到系列3、6、18、24，…的N个项

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：

3, 6, 18, 24, 45, 54...(Nth term)

例子：

Input: N = 5
Output: 45
Explanation:
For N = 5,
Nth term = ( N * ( (N/2) + ( (N%2) * 2) + N ) 
         = ( 5 * ( (5/2) + ( (5%2) * 2) + 5 ) 
         = ( 5 * ( 2 + ( 1 * 2) + 5 )
         = 45

Input : 6 
Output : 54

该系列的广义第N个术语：

Nth term = ( N * ( (N/2) + ((N%2) * 2) + N )

下面是上述方法的实现：

C++

// CPP program to find N-th term of the series:
// 3, 6, 18, 24, 45, 54...
 
#include 
using namespace std;
 
// function to calculate Nth term of series
int nthTerm(int N)
{
    // By using above formula
    return (N * ((N / 2) + ((N % 2) * 2) + N));
}
 
// Driver Function
int main()
{
 
    // get the value of N
    int N = 5;
 
    // Calculate and print the Nth term
    cout << "Nth term for N = "
         << N << " : "
         << nthTerm(N);
 
    return 0;
}

Java

import java.io.*;
 
// Class to calculate Nth term of series
class Nth {
    public int nthTerm(int N)
    {
        // By using above formula
        return (N * ((N / 2) + ((N % 2) * 2) + N));
    }
}
 
// Main class for main method
class GFG {
 
    public static void main(String[] args)
    {
 
        // get the value of N
        int N = 5;
 
        // create object of Class Nth
        Nth a = new Nth();
 
        // Calculate and print the Nth term
        System.out.println("Nth term for N = "
                           + N + " : "
                           + a.nthTerm(N));
    }
}

Python3

# Python3 program to find N-th term of the series:
# 3, 6, 18, 24, 45, 54...
 
 
# function to calculate Nth term of series
def nthTerm( N):
    # By using above formula
    return (N * ((N // 2) + ((N % 2) * 2) + N))
 
 
# Driver Function
 
# get the value of N
if __name__=='__main__':
    N = 5
 
    # Calculate and print the Nth term
    print( "Nth term for N = ", N ," : ", nthTerm(N))
 
 
# This code is contributed by ash264

C#

// C# program to find N-th
// term of the series:
// 3, 6, 18, 24, 45, 54...
using System;
 
class GFG
{
public int nthTerm(int N)
{
    // By using above formula
    return (N * ((N / 2) +
           ((N % 2) * 2) + N));
}
 
// Driver Code
public static void Main()
{
 
    // get the value of N
    int N = 5;
 
    // create object of Class Nth
    GFG a = new GFG();
 
    // Calculate and print the Nth term
    Console.WriteLine("Nth term for N = " +
                                N + " : " +
                             a.nthTerm(N));
}
}
 
// This code is contributed
// by inder_verma..

Javascript

// JavaScript program to find N-th term of the series:
// 3, 6, 18, 24, 45, 54...
 
// function to calculate Nth term of series
function nthTerm( N)
{
    // By using above formula
    return parseInt(N * (parseInt(N / 2) + ((N % 2) * 2) + N));
}
  
// Driver Function
 
    // get the value of N
    let N = 5;
 
    // Calculate and print the Nth term
    document.write( "Nth term for N = "
         + N +" : "
         + nthTerm(N));
 
// This code is contributed by todaysgaurav
 

输出：

Nth term for N = 5 : 45

时间复杂度： O(1)