摘要：Lattice paths Problem 15 Problem 15 Starting in the top left corner of a 2×2 grid, and only being able to move to the right and down, there are exactl 阅读全文

摘要：By Lu.Qian. Question: Longest Collatz sequence Problem 14 Problem 14 The following iterative sequence is defined for the set of positive integers: n → 阅读全文

摘要：Largest prime factor Problem 3 Problem 3 The prime factors of 13195 are 5, 7, 13 and 29. What is the largest prime factor of the number 600851475143 ? 阅读全文

摘要：Smallest multiple Problem 5 Problem 5 2520 is the smallest number that can be divided by each of the numbers from 1 to 10 without any remainder. What 阅读全文