摘要： Fibonotci sequence is an integer recursive sequence defined by the recurrence relation Fn = sn - 1·Fn - 1 + sn - 2·Fn - 2withF0 = 0, F1 = 1 Sequence s 阅读全文

摘要： For a sequence a of n integers between 1 and m, inclusive, denote f(a) as the number of distinct subsequences of a (including the empty subsequence). 阅读全文

摘要： Little X has met the following problem recently. Let's define f(x) as the sum of digits in decimal representation of number x (for example, f(1234) =  阅读全文