求数列 3、7、19、55、163、.。。

原文:https://www . geesforgeks . org/find-the-n-term-of-series-3-7-19-55-163/

给定正整数 N 。任务是找到系列 3，7，19，55，163 的第 n 个术语..

示例:

输入 : N = 5 输出 : 163

输入 : N = 1 输出 : 3

逼近:使用以下模式形成序列。对于任何 N 值

t_N= 2 * 3^N–1+1

插图:

输入: N = 5 输出: 163 解释: T_N= 2 * 3^N–1+1 = 2 * 3^5–1+1 = 2 * 81+1 = 162+1 = 163

下面是上述方法的实现:

C++

// C++ program to implement
// the above approach
#include <bits/stdc++.h>
using namespace std;

// Function to return Nth term
// of the series
int calcNum(int N)
{
    return 2 * pow(3, N - 1) + 1;
}

// Driver Code
int main()
{
    int N = 5;
    cout << calcNum(N);
    return 0;
}

Python 3

# Python3 program to implement
# the above approach

# Function to return Nth term
# of the series
def calcNum(N):

    return 2 * (3 ** (N - 1)) + 1

# Driver Code
N = 5

print(calcNum(N))

# This code is contributed by gfgking

java 描述语言

<script>
      // JavaScript code for the above approach

      // Function to return Nth term
      // of the series
      function calcNum(N) {
          return 2 * Math.pow(3, N - 1) + 1;
      }

      // Driver Code

      let N = 5;
      document.write(calcNum(N));

// This code is contributed by Potta Lokesh
  </script>

Output

163

时间复杂度: O(1)

辅助空间: O(1)

---

版权属于：月萌API www.moonapi.com，转载请注明出处

本文链接：https://moonapi.com/news/34487.html