Some of the best features that came with LINQ that isn't related to databases.

program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;

namespace DummyConsole
{
  internal unsafe class Program
  {
    public static void Main(string[] args) { (new Program()).Run(); }


    public void Run()
    {
      Console.Write("Enter condition: ");
      var predicate = predicatize(Console.ReadLine());

      Console.Write("  Understood as: ");
      Console.WriteLine(predicate.ToString());

      Console.WriteLine("Displaying the first 10 results:");
      var results = fib()
        .AsParallel()
        .Where((_, idx) => idx < 10000) // limit search space
        .Where(predicate.Compile())
        .Take(10);

      foreach (var num in results)
        Console.WriteLine(num);

      Console.WriteLine("Done.");
      Console.ReadKey();
    }

    private IEnumerable<int> fib()
    {
      int a = 0, b = 1;
      while (true)
        yield return a = b + (b = a);
    }

    private Expression<Func<int, bool>> predicatize(string str)
    {
      var arg = Expression.Parameter(typeof(int), "n");
      return Expression.Lambda<Func<int, bool>>(predicatizeCore(str, arg), arg);
    }

    private Expression predicatizeCore(string str, Expression arg)
    {
      var idx = -1;

      Func<string, Func<Expression, Expression, Expression>, Expression> binOps =
        (op, builder) =>
          (idx = str.IndexOf(op)) > -1 ? builder(
            predicatizeCore(str.Substring(0, idx), arg),
            predicatizeCore(str.Substring(idx + op.Length), arg)) :
          null;

      return string.IsNullOrEmpty(str = str.Trim()) ? Expression.Constant(false) :
        char.IsNumber(str[0]) ? Expression.Constant(int.Parse(str)) : (
        binOps("&&", Expression.And) ??
        binOps("||", Expression.Or) ??
        binOps("<", Expression.LessThan) ??
        binOps(">", Expression.GreaterThan) ??
        binOps("==", Expression.Equal) ??
        binOps("!=", Expression.NotEqual) ??
        arg);
    }
  }
}

sample result.txt

Enter condition: n < 8 || n > 100000 && n != 1
  Understood as: n => (((n < 8) Or (n > 100000)) And (n != 1))
Displaying the first 10 results:
2
3
5
121393
196418
317811
514229
832040
1346269
2178309
Done.