程序以找到系列3、20、63、144、230，……的第N个术语

给定一个序列和一个数字N。任务是找到给定序列的第N个术语：

3, 20, 63, 144, 230 …..

例子：

Input: N = 4
Output: 144
When n = 4
nth term = 2 ( n * n * n ) + n * n
         = 2 ( 4 * 4 * 4 ) + 4 * 4
         = 144

Input: N = 10
Output: 2100

方法：我们可以找到给定序列的一般术语(Tn)。
$series\: can\: be\: written\: in\: the\: following\: way\: also:\\ (3 * 1^2), (5 * 2^2), (7 * 3^2), (9 * 4^2), .......up t n terms\\ Tn = (\:General\; term\; of \;series\; 3, 5, 7, 9 ....\;)\; X\; (\;General\; term\; of\; series\; 1^2, 2^2, 3^2, 4^2 ....\;)\\ Tn = (3 + (n-1) * 2) X ( n^2 )\\ Tn = 2*n^3 + n^2$
以下是所需的实现：

C++

// CPP program to find N-th term of the series:
// 3, 20, 63, 144, 230 .....
#include 
#include 
using namespace std;
 
// calculate Nth term of series
int nthTerm(int n)
{
    return 2 * pow(n, 3) + pow(n, 2);
}
 
// Driver code
int main()
{
    int N = 3;
 
    cout << nthTerm(N);
 
    return 0;
}

Java

// Java program to find N-th term of the series:
// 3, 20, 63, 144, 230 .....
import java.util.*;
 
class solution
{
 
// calculate Nth term of series
static int nthTerm(int n)
{
    //return final sum
    return 2 *(int)Math.pow(n, 3) + (int)Math.pow(n, 2);
}
 
// Driver code
public static void main(String arr[])
{
    int N = 3;
 
System.out.println(nthTerm(N));
 
}
 
}
//This code is contributed by Surendra_Gangwar

Python 3

# Python program to find
# N-th term of the series:
# 3, 20, 63, 144, 230 .....
 
# calculate Nth term of series
def nthTerm(n) :
 
    return 2 * pow(n, 3) + pow(n, 2)
 
# Driver code
if __name__ == "__main__" :
 
    N = 3
    print(nthTerm(N))
 
# This code is contributed
# by ANKITRAI1

C#

// C# program to find N-th term of the series:
// 3, 20, 63, 144, 230 .....
using System;
 
class solution
{
 
// calculate Nth term of series
static int nthTerm(int n)
{
    //return final sum
    return 2 *(int)Math.Pow(n, 3) + (int)Math.Pow(n, 2);
}
 
// Driver code
public static void Main()
{
    int N = 3;
 
Console.WriteLine(nthTerm(N));
 
}
 
}
//This code is contributed by  Shashank

Javascript

 
// JavaScript program to find N-th term of the series:
// 3, 20, 63, 144, 230 .....
 
// calculate Nth term of series
function nthTerm( n)
{
    return 2 * Math.pow(n, 3) + Math.pow(n, 2);
}
 
 
// Driver code
 
    let N = 3;
   document.write( nthTerm(N) );
 
// This code contributed by aashish1995
 

输出：

63

时间复杂度： O(1)