欧拉编程
http://projecteuler.net/index.php上有很多题，等着大家编程练手。
应该不会很难的？ nice job
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Problem 262 will be accessible in 1 day, 9 hours, 19 minutes (Fri 30 Oct 2009 at 9.00 pm )
Current date/time on server: Thu 29 Oct 2009 11.41 am
Page: 123456
ID Description / Title Solved By
1 Add all the natural numbers below one thousand that are multiples of 3 or 5. 76780
2 Find the sum of all the even-valued terms in the Fibonacci sequence which do not exceed four million. 64264
3 Find the largest prime factor of a composite number. 47019
4 Find the largest palindrome made from the product of two 3-digit numbers. 43904
5 What is the smallest number divisible by each of the numbers 1 to 20? 50238
6 What is the difference between the sum of the squares and the square of the sums? 51431
7 Find the 10001st prime. 42838
8 Discover the largest product of five consecutive digits in the 1000-digit number. 38556
9 Find the only Pythagorean triplet, {a, b, c}, for which a + b + c = 1000. 38302
10 Calculate the sum of all the primes below two million. 34612
11 What is the greatest product of four numbers on the same straight line in the 20 by 20 grid? 26717
12 What is the value of the first triangle number to have over five hundred divisors? 22862
13 Find the first ten digits of the sum of one-hundred 50-digit numbers. 27166
14 Find the longest sequence using a starting number under one million. 25679
15 Starting in the top left corner in a 20 by 20 grid, how many routes are there to the bottom right corner? 21054
16 What is the sum of the digits of the number 21000? 28406
17 How many letters would be needed to write all the numbers in words from 1 to 1000? 17844
18 Find the maximum sum travelling from the top of the triangle to the base. 18181
19 How many Sundays fell on the first of the month during the twentieth century? 16723
20 Find the sum of digits in 100! 27379
21 Evaluate the sum of all amicable pairs under 10000. 18052
22 What is the total of all the name scores in the file of first names? 17144
23 Find the sum of all the positive integers which cannot be written as the sum of two abundant numbers. 11879
24 What is the millionth lexicographic permutation of the digits 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9? 14789
25 What is the first term in the Fibonacci sequence to contain 1000 digits? 21276
26 Find the value of d < 1000 for which 1/d contains the longest recurring cycle. 10289
27 Find a quadratic formula that produces the maximum number of primes for consecutive values of n. 10750
28 What is the sum of both diagonals in a 1001 by 1001 spiral? 16330
29 How many distinct terms are in the sequence generated by ab for 2 ≤ a ≤ 100 and 2 ≤ b ≤ 100? 13445
30 Find the sum of all the numbers that can be written as the sum of fifth powers of their digits. 15024
31 Investigating combinations of English currency denominations. 10181
32 Find the sum of all numbers that can be written as pandigital products. 8636
33 Discover all the fractions with an unorthodox cancelling method. 9645
34 Find the sum of all numbers which are equal to the sum of the factorial of their digits. 13190
35 How many circular primes are there below one million? 11970
36 Find the sum of all numbers less than one million, which are palindromic in base 10 and base 2. 13471
37 Find the sum of all eleven primes that are both truncatable from left to right and right to left. 9774
38 What is the largest 1 to 9 pandigital that can be formed by multiplying a fixed number by 1, 2, 3, ... ? 8067
39 If p is the perimeter of a right angle triangle, {a, b, c}, which value, for p ≤ 1000, has the most solutions? 9726
40 Finding the nth digit of the fractional part of the irrational number. 11562
41 What is the largest n-digit pandigital prime that exists? 8973
42 How many triangle words does the list of common English words contain? 11075
43 Find the sum of all pandigital numbers with an unusual sub-string divisibility property. 7287
44 Find the smallest pair of pentagonal numbers whose sum and difference is pentagonal. 6932
45 After 40755, what is the next triangle number that is also pentagonal and hexagonal? 10382
46 What is the smallest odd composite that cannot be written as the sum of a prime and twice a square? 7298
47 Find the first four consecutive integers to have four distinct primes factors. 7428
48 Find the last ten digits of 11 + 22 + ... + 10001000. 18629
49 Find arithmetic sequences, made of prime terms, whose four digits are permutations of each other. 7102
50 Which prime, below one-million, can be written as the sum of the most consecutive primes? 7643
Page: 123456
Project Euler Copyright Information 那里不光靠编程，还是需要动动脑子找点方法的，否则那些大数够你跑的，或者要找个好点的工具。
曾经迷恋Ruby的时候上去做了87道题，现在总数都快262了。 呵呵，难度不小的。
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