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public class Solution
{
private static bool[] prime = null;
public static void Main(string[] args)
{
int numberOfTestCases = int.Parse(Console.ReadLine());
GeneratePrimes();
for (int i = 0; i < numberOfTestCases; i++)
{
int res = 0;
int n = int.Parse(Console.ReadLine());
for (int j = 2; j <= n; j++)
{
if (prime[j])
{
int diff = n - j;
if (diff % 2 == 0 && IsPerfectSquare(diff / 2))
res += 1;
}
}
Console.WriteLine(res);
}
}
public static bool IsPerfectSquare(int input)
{
int root = (int)Math.Sqrt(input);
return input == root * root;
}
public static void GeneratePrimes()
{
int limit = 1000000;
prime = new bool[limit + 1];
prime[2] = true;
prime[3] = true;
int root = (int)Math.Ceiling(Math.Sqrt(limit));
// Sieve of Atkin for prime number generation
for (int x = 1; x < root; x++)
{
for (int y = 1; y < root; y++)
{
int n = 4 * x * x + y * y;
if (n <= limit && (n % 12 == 1 || n % 12 == 5))
prime[n] = !prime[n];
n = 3 * x * x + y * y;
if (n <= limit && n % 12 == 7)
prime[n] = !prime[n];
n = 3 * x * x - y * y;
if ((x > y) && (n <= limit) && (n % 12 == 11))
prime[n] = !prime[n];
}
}
for (int i = 5; i <= root; i++)
{
if (prime[i])
{
for (int j = i * i; j < limit; j += i * i)
{
prime[j] = false;
}
}
}
}
}
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Project Euler #46: Goldbach's other conjecture
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C#
using System;
public class Solution { private static bool[] prime = null;
}