Question

How to find the first 10 prime Fibonacci numbers in C#

Answer 1

using System;

class PrimeFibonacci
{
    static bool IsPrime(long n)
    {
        if (n < 2) return false;
        if (n == 2 || n == 3) return true;
        if (n % 2 == 0) return false;

        for (long i = 3; i * i <= n; i += 2)
            if (n % i == 0)
                return false;

        return true;
    }

    static long NextFib(ref long a, ref long b)
    {
        long f = a;
        long next = a + b;
        a = b;
        b = next;

        return f;
    }

    static void Main()
    {
        long a = 1, b = 1;
        int count = 0;

        while (count < 10) {
            long f = NextFib(ref a, ref b);
            if (IsPrime(f)) {
                Console.Write(f + " ");
                count++;
            }
        }
    }
}



/*
run:

2 3 5 13 89 233 1597 28657 514229 433494437 

*/

 

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