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Newman–Shanks–Williams prime

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In mathematics, a Newman–Shanks–Williams prime (NSW prime) is a prime number p which can be written in the form: 

{\huge S_{2m+1} = \frac{ {(1+\sqrt{2})^{2m+1} + (1-\sqrt{2})^{2m+1} } }{2} }

The recurrence relation for Newman–Shanks–Williams prime is
S_0 = 1
S_1 = 1
S_n = 2*S_{n-1} + S{n-2}
The first few terms of the sequence are 1, 1, 3, 7, 17, 41, 99,…

Examples: 

Input : n = 3
Output : 7

Input : n = 4
Output : 17 

Below is the implementation of finding nth Newman–Shanks–Williams prime: 

C++

// CPP Program to find Newman–Shanks–Williams prime
#include <bits/stdc++.h>
using namespace std;
 
// return nth Newman–Shanks–Williams prime
int nswp(int n)
{
    // Base case
    if (n == 0 || n == 1)
        return 1;
 
    // Recursive step
    return 2 * nswp(n - 1) + nswp(n - 2);
}
 
// Driven Program
int main()
{
    int n = 3;
 
    cout << nswp(n) << endl;
    return 0;
}

                    

Java

// Java Program to find
// Newman-Shanks-Williams prime
import java.io.*;
 
class GFG
{
// return nth Newman-Shanks-Williams
// prime
static int nswp(int n)
{
    // Base case
    if (n == 0 || n == 1)
        return 1;
 
    // Recursive step
    return 2 * nswp(n - 1) + nswp(n - 2);
}
 
// Driver code
public static void main (String[] args)
{
    int n = 3;
    System.out.println(nswp(n));
}
}
 
// This code is contributed by Anant Agarwal.

                    

Python3

# Python3 Program to find Newman–Shanks–Williams prime
 
# return nth Newman–Shanks–Williams prime
def nswp(n):
     
    # Base case
    if n == 0 or n == 1:
        return 1
 
    # Recursive step
    return 2 * nswp(n - 1) + nswp(n - 2)
 
# Driven Program
n = 3
print (nswp(n))
 
 
# This code is contributed by Shreyanshi Arun.

                    

C#

// C# Program to find
// Newman-Shanks-Williams prime
using System;
 
class GFG {
     
    // return nth Newman-Shanks-Williams
    // prime
    static int nswp(int n)
    {
         
        // Base case
        if (n == 0 || n == 1)
            return 1;
 
        // Recursive step
        return 2 * nswp(n - 1) + nswp(n - 2);
    }
 
    // Driver code
    public static void Main()
    {
        int n = 3;
         
        Console.WriteLine(nswp(n));
    }
}
 
// This code is contributed by vt_m.

                    

PHP

<?php
// PHP Program to find
// Newman–Shanks–Williams prime
 
// return nth Newman –
// Shanks – Williams prime
function nswp($n)
{
     
    // Base case
    if ($n == 0 || $n == 1)
        return 1;
 
    // Recursive step
    return 2 * nswp($n - 1) +
               nswp($n - 2);
}
 
// Driver Code
$n = 3;
echo(nswp($n));
 
// This code is contributed by Ajit.
?>

                    

Javascript

<script>
    // Javascript Program to find Newman-Shanks-Williams prime
     
    // return nth Newman-Shanks-Williams
    // prime
    function nswp(n)
    {
           
        // Base case
        if (n == 0 || n == 1)
            return 1;
   
        // Recursive step
        return 2 * nswp(n - 1) + nswp(n - 2);
    }
     
    let n = 3;
           
      document.write(nswp(n));
      
     // This code is contributed by mukesh07.
</script>

                    

Output
7

Time Complexity: O(2n)
Auxiliary Space: O(1)

Below is the Dynamic Programming solution of finding nth Newman–Shanks–Williams prime: 

C++

// CPP Program to find Newman–Shanks–Williams prime
#include <bits/stdc++.h>
using namespace std;
 
// return nth Newman–Shanks–Williams prime
int nswp(int n)
{
    int dp[n + 1];
 
    // Base case
    dp[0] = dp[1] = 1;
 
    // Finding nth Newman–Shanks–Williams prime
    for (int i = 2; i <= n; i++)
        dp[i] = 2 * dp[i - 1] + dp[i - 2];
 
    return dp[n];
}
 
// Driver Program
int main()
{
    int n = 3;
 
    cout << nswp(n) << endl;
    return 0;
}

                    

Java

// Java Program for finding
// Newman-Shanks-Williams prime
import java.util.*;
 
class GFG
{
    // return nth Newman_Shanks_Williams prime
    public static int nswpn(int n)
    {
        int dp[] = new int[n + 1];
         
        // Base case
        dp[0] = dp[1] = 1;
         
        // Finding nth Newman_Shanks_Williams prime
        for (int i = 2; i <= n; i++)
          dp[i] = 2 * dp[i - 1] + dp[i - 2];
         
        return dp[n];
    }
     
    // Driver Program
    public static void main (String[] args) {
         
        int n = 3;
         
        System.out.println(nswpn(n));
    }
}
 
/* This code is contributed by Akash Singh */

                    

Python3

# Python3 Program to find
# Newman–Shanks–Williams prime
 
# return nth Newman–Shanks
# –Williams prime
def nswp(n):
     
    # Base case
    dp = [1 for x in range(n + 1)];
     
    # Finding nth Newman–Shanks
    # –Williams prime
    for i in range(2, n + 1):
        dp[i] = (2 * dp[i - 1] +
                     dp[i - 2]);
    return dp[n];
 
# Driver Code
n = 3;
print(nswp(n));
 
# This code is contributed
# by mits

                    

C#

// C# Program to find Newman–Shanks–Williams prime
 
using System;
 
class GFG {
 
    // return nth Newman–Shanks–Williams prime
    static int nswp(int n)
    {
         
        int[] dp = new int[n + 1];
 
        // Base case
        dp[0] = dp[1] = 1;
 
        // Finding nth Newman–Shanks–Williams prime
        for (int i = 2; i <= n; i++)
            dp[i] = 2 * dp[i - 1] + dp[i - 2];
 
        return dp[n];
    }
 
    // Driver Program
    public static void Main()
    {
        int n = 3;
 
        Console.WriteLine(nswp(n));
    }
}
 
// This code is contributed by vt_m.

                    

PHP

<?php
// PHP Program to find
// Newman–Shanks–Williams prime
 
// return nth Newman–Shanks
// –Williams prime
function nswp($n)
{
     
    // Base case
    $dp[0] = $dp[1] = 1;
 
    // Finding nth Newman–Shanks
    // –Williams prime
    for ($i = 2; $i <= $n; $i++)
        $dp[$i] = 2 * $dp[$i - 1] +
                      $dp[$i - 2];
 
    return $dp[$n];
}
 
// Driver Code
$n = 3;
echo(nswp($n));
 
// This code is contributed by Ajit.
?>

                    

Javascript

<script>
 
    // Javascript Program to find
    // Newman–Shanks–Williams prime
     
    // return nth Newman–Shanks–Williams prime
    function nswp(n)
    {
          
        let dp = new Array(n + 1);
  
        // Base case
        dp[0] = dp[1] = 1;
  
        // Finding nth Newman–Shanks–Williams prime
        for (let i = 2; i <= n; i++)
            dp[i] = 2 * dp[i - 1] + dp[i - 2];
  
        return dp[n];
    }
     
    let n = 3;
      document.write(nswp(n));
         
</script>

                    

Output
7

Time Complexity: O(n)
Auxiliary Space: O(n)

Below is the code with O(1) space complexity  

C++

// C++ code
#include <iostream>
using namespace std;
 
int nswp(int n)
{
     
    if(n == 0 || n == 1)
    {
        return 1;
    }
     
    // Here we only need to store last 2 values
    // to find the value of n,
    // so we will store those 2 values only.
    int a = 1, b = 1;
     
    for(int i = 2; i <= n; ++i)
    {
        int c = 2 * b + a;
        a = b;
        b = c;
    }
    return b;
}
int main()
{
    int n = 3;
    cout << nswp(n);
    return 0;
}
 
// This code is contributed by SHUBHAMSINGH10

                    

Java

// Write Java code here
import java.io.*;
class GFG {
    static int nswp(int n)
    {
        if (n == 0 || n == 1)
            return 1;
        // Here we only need to store last 2 values to find
        // the value of n, so we will store those 2 values
        // only.
        int a = 1, b = 1;
        for (int i = 2; i <= n; ++i) {
            int c = 2 * b + a;
            a = b;
            b = c;
        }
        return b;
    }
    public static void main(String[] args)
    {
        int n = 3;
        System.out.println(nswp(n));
    }
}

                    

Python3

# Write Python3 code here
 
def nswp(n):
    if(n<2): return 1
    a,b=1,1
    for i in range(2,n+1):
        c=2*b+a
        a=b
        b=c
    return b
n=3
print(nswp(n))

                    

C#

// C# code
using System;
 
class GFG
{
    static int nswp(int n) {
        if (n == 0 || n == 1)
            return 1;
             
        // Here we only need to store last 2 values
        // to find the value of n,
        // so we will store those 2 values only.
        int a = 1, b = 1;
        for (int i = 2; i <= n; ++i) {
            int c = 2 * b + a;
            a = b;
            b = c;
        }
        return b;
    }
 
    public static void Main(String[] args)
    {
        int n = 3;
        Console.WriteLine(nswp(n));
    }
}
 
// This code is contributed by PrinciRaj1992

                    

Javascript

<script>
    // Javascript code
     
    function nswp(n) {
        if (n == 0 || n == 1)
            return 1;
              
        // Here we only need to store last 2 values
        // to find the value of n,
        // so we will store those 2 values only.
        let a = 1, b = 1;
        for (let i = 2; i <= n; ++i) {
            let c = 2 * b + a;
            a = b;
            b = c;
        }
        return b;
    }
     
    let n = 3;
      document.write(nswp(n));
     
</script>

                    

Output
7

Time Complexity: O(n)
Auxiliary Space: O(1)
 



Last Updated : 13 Jan, 2023
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