How many ways are there to choose a 5-letter word from the 26-letter English alphabet with replacement, where words that are anagrams are considered the same?
Prove F2n+1 − F2n = Fn−1Fn+2 for n ≥ 1.
Prove that for any given 55 integers, one can choose 10 of the integers such that the difference of any two of them is divisible by 6.
Sample Solution