public class MakeEffort {
    public static void main(String[] args) {
        int a, b, c, d, e, f;
        for (a = 1; a <= 9; ++a) {
            for (b = 2; b <= 8; b += 2) {
                if (a != b) {
                    for (c = 1; c <= 9; ++c) {
                        if (c != a && c != b) {
                            for (d = 2; d <= 8; d += 2) {
                                if (d != a && d != b && d != c) {
                                    for (e = 1; e <= 9; ++e) {
                                        if (e != a && e != b && e != c && e != d) {
                                            for (f = 1; f <= 9; ++f) {
                                                if ((2*(a*100000 + b*10000 + c*1000 + d*100 + e*10 + f) ==
                                                    (c*100000 + d*10000 + e*1000 + f*100 + a*10 + b)) &&
                                                    (2*(c*100000 + d*10000 + e*1000 + f*100 + a*10 + b)) ==
                                                    (e*100000 + f*10000 + a*1000 + b*100 + c*10 + d)) {
                                                    System.out.println("a = " + a + ", b = " + b + ", c = " + c +
                                                                       ", d = " + d + ", e = " + e + ", f = " + f);
                                                }
                                            }
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}

------解决方案--------------------

ABCDEF 是142857
Java code


import java.util.Arrays;

/**
 * Created by IntelliJ IDEA.
 * User: Administrator
 * Date: 2011-10-1
 * Time: 21:32:15
 * To change this template use File | Settings | File Templates.
 */
public class PuzzleDemo {
    /**
     *
     * @param num
     * @return
     */
    public static char[] parse(int num){
        char[] result=new char[6];
        String s=Integer.toString(num);
        for(int i=0;i<6;i++){
            result[i]=s.charAt(i);
        }
        return result;
    }

    public static void main(String[] args) {
//        char[] char1=parse(123456);
//        char[] char2=new char[6];
//        char[] char3=new char[6];
//
//        for(int j=0;j<6;j++){
//            int aa=(j+2)%6;
//            char2[j]=char1[aa];
//        }
//        for(int j=0;j<6;j++){
//            int aa=(j+4)%6;
//            char3[j]=char1[aa];
//        }
//        String s1=new String(char1);
//        String s2=new String(char2);
//        String s3=new String(char3);
//        System.out.println(s1);
//        System.out.println(s2);
//        System.out.println(s3);
//        System.out.println("解析："+ Arrays.toString(char1));
//        System.out.println("解析："+ Arrays.toString(char2));
//        System.out.println("解析："+ Arrays.toString(char3));
        for(int i=100000;i<999999;i++){
            char[] char1=parse(i);
            char[] char2=new char[6];
            for(int j=0;j<6;j++){
                int aa=(j+2)%6;
                char2[j]=char1[aa];
            }
            char[] char3=new char[6];
            for(int j=0;j<6;j++){
                int aa=(j+4)%6;
                char3[j]=char1[aa];
            }
            String s1=new String(char1);
            String s2=new String(char2);
            String s3=new String(char3);
            int i2=Integer.parseInt(s2);
            int i3=Integer.parseInt(s3);
            if(i*2==i2&&i2*2==i3){
                //这里还需要检查6位数字是否重复 ,因为不写也只有一个结果，没写
//                for(){
//
//                }
                  System.out.println(i);
            }
        }
    }
}