quark

摘要： Problem DescriptionThere are exactly ten ways of selecting three from five, 12345:123, 124, 125, 134, 135, 145, 234, 235, 245, and 345In combinatorics, we use the notation, 5C3= 10.In general,nCr =n!r!(n-r)!,where r<=n, n! = n*(n-1)…*3*2*1, and 0! = 1.It is not until n = 23, that a value exceeds 阅读全文

摘要： Problem Description It can be seen that the number, 125874, and its double, 251748, contain exactly the same digits, but in a different order. Find the smallest positive integer, x, such that 2x, 3x, ... 阅读全文