xiaoman111的专栏

<br />We shall say that an n-digit number is pandigital if it makes use of  all the digits 1 to n exactly once; for example, the 5-digit number,  15234, is 1 through 5 pandigital.<br /><br /> The product 7254 is unusual, as the identity, 39*186 = 7254, con

原题：A googol (power(10,100)) is a massive number: one followed by one-hundred zeros;  power(100,100) is almost unimaginably large: one followed by two-hundred zeros.  Despite their size, the sum of t

原题：Starting with 1 and spiralling anticlockwise in the following way, a square spiral with side length 7 is formed. 37 36 35 34 33 32 31 38 17 16 15 14 13 30 39 18 5 4 3 12 29 40 19 6 1 2

原题： //合数是与质数（也叫素数）相对应的概念，即除了1和本身之外，还可以被其它正整数整除的数称为合数。 //奇合数：既是合数又是奇数的数称为奇合数。例如：9，15，21等等都是奇合数。 It was proposed by Christian Goldbach that every odd composite number can be written as   the sum of a

原题：Triangle, pentagonal, and hexagonal numbers are generated by the following formulae: * Triangle T(n)=n(n+1)/2 1, 3, 6, 10, 15, ... Pentagonal P(n)=n(3n-1)/2 1, 5, 12, 22, 35, ... Hexagon

原题：Pentagonal numbers are generated by the formula, Pn=n(3n-1)/2.  The first ten pentagonal numbers are: 1, 5, 12, 22, 35, 51, 70, 92, 117, 145, ... It can be seen that P4 + P7 = 22 + 70 = 92 = P8.

原题：We shall say that an n-digit number is pandigital  if it makes use of all the digits 1 to n exactly once.  For example, 2143 is a 4-digit pandigital and is also prime. What is the largest n-digit

原题：An irrational decimal(无理小数) fraction is created by concatenating the positive integers: 0.123456789101112131415161718192021... It can be seen that the 12(th) digit of the fractional part is 1. If

原题：The nth term of the sequence of triangle numbers is given by, t(n) = 1/2*n(n+1); so the first ten triangle numbers are: 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, ...  By converting each letter in a wo

原题：If p is the perimeter of a right angle triangle with integral length sides,  {a,b,c}, there are exactly three solutions for p = 120.{20,48,52}, {24,45,51}, {30,40,50} For which value of p分析：由

原题：Take the number 192 and multiply it by each of 1, 2, and 3: 192*1 = 192 192*2 = 384 192*3 = 576 By concatenating each product we get the 1 to 9 pandigital, 192384576. We will call 192384576 the

原题：The number 3797 has an interesting property. Being prime itself,   it is possible to continuously remove digits from left to right, and remain prime at each stage: 3797, 797, 97, and 7. Similarly w

原题：The decimal number, 585 = 1001001001 (binary), is palindromic in both bases. Find the sum of all numbers, less than one million, which are palindromic in base 10 and base 2. (Please note that the

 Starting with the number 1 and moving to the right in a clockwise  direction a 5 by 5 spiral is formed as follows: 21 22 23 24 25   20 7 8 9 10   19 6 1 2 11   18 5 4 3 12 17 16 15 14 13 It can be verified that the sum of the numbers on th

<br />package cn.javass.mytest.java.euler; import java.util.Set; import java.util.TreeSet; /** * a(b) 表示 a的b次方 * * Consider all integer combinations of ab for 2<=a<=5 and 2<=b<=5: 2(2)=4, 2(3)=8, 2(4)=16, 2(5)=32 3(2)=9, 3(3)=27,

原题：145 is a curious number, as 1! + 4! + 5! = 1 + 24 + 120 = 145.Find the sum of all numbers which are equal to the sum of the factorial of their digits. Note: as 1! = 1 and 2! = 2 are not sums they

原题：The number, 197, is called a circular prime because all rotations of the digits:   197, 971, and 719, are themselves prime. There are thirteen such primes below 100: 2, 3, 5, 7, 11, 13, 17, 31,

原题：It is possible to show that the square root of two can be expressed as an infinite continued fraction. 2(开方) = 1 + 1/(2 + 1/(2 + 1/(2 + ... ))) = 1.414213... By expanding this for the first fou