程序以找到系列3、12、29、54、87，…的N个项

给定数字N，任务是找到该系列的第N个项：

3, 12, 29, 54, 87, ………….

例子：

Input: N = 4
Output: 54
Explanation:
Nth term = 4 * pow(n, 2) - 3 * n + 2
         = 4 * pow(4, 2) - 3 * 4 + 2
         = 54

Input: N = 10
Output: 372

方法：
给定系列的第N个术语是：

系列的第N个词$T_n = 4 * n * n - 3 * n + 2$ [Tex] [/ Tex]

下面是上述方法的实现：

C++

// CPP program to find N-th term of the series:
// 3, 12, 29, 54, 87, ...
 
#include 
#include 
using namespace std;
 
// calculate Nth term of series
int getNthTerm(long long int N)
{
    // Return Nth term
    return 4 * pow(N, 2) - 3 * N + 2;
}
 
// driver code
int main()
{
    // declaration of number of terms
    long long int N = 10;
 
    // Get the Nth term
    cout << getNthTerm(N);
 
    return 0;
}

Java

// Java program to find N-th term of the series:
// 3, 12, 29, 54, 87, ...
 
import java.util.*;
class solution
{
 
static long getNthTerm(long N)
{
    // Return Nth term
    return 4 *(long)Math.pow(N, 2) - 3 * N + 2;
}
 
//Driver code
public static void main(String arr[])
{
// declaration of number of terms
    long N = 10;
 
    // Get the Nth term
    System.out.println(getNthTerm(N));
 
}
}

Python3

# Python3 program to find N-th term of the series:
# 3, 12, 29, 54, 87, ...
 
# calculate Nth term of series
def getNthTerm(N):
 
    # Return Nth term
    return 4 * pow(N, 2) - 3 * N + 2
 
# driver code
if __name__=='__main__':
     
    # declaration of number of terms
    N = 10
 
    # Get the Nth term
    print(getNthTerm(N))
 
# This code is contributed by
# Sanjit_Prasad

C#

// C# program to find
// N-th term of the series:
// 3, 12, 29, 54, 87, ...
using System;
 
class GFG
{
static long getNthTerm(long N)
{
    // Return Nth term
    return 4 * (long)Math.Pow(N, 2) -
                         3 * N + 2;
}
 
// Driver code
static public void Main ()
{
 
    // declaration of number
    // of terms
    long N = 10;
     
    // Get the Nth term
    Console.Write(getNthTerm(N));
}
}
 
// This code is contributed by Raj

Javascript

 
// javascript program to find N-th term of the series:
// 3, 12, 29, 54, 87, ...
 
 
// calculate Nth term of series
function getNthTerm( N)
{
    // Return Nth term
    return 4 * Math.pow(N, 2) - 3 * N + 2;
}
 
// driver code
 
    // declaration of number of terms
    let N = 10;
 
    // Get the Nth term
    document.write( getNthTerm(N));
     
// This code contributed by gauravrajput1
 

输出：

372

时间复杂度： O(1)