The number of ways to choose a subset of two elements {a, b} from the set {1, 2, 3, 4, \ldots, 49, 50} such that |a - b| \leq 5 is
The sequence of all positive palindromes are written in ascending order: 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, ...Then the 2018th positive palindrome is
In how many ways can a word of five letters beginning with a capital letter and consisting of two vowels and two consonants be formed with the capital letters C, A, C; vowels o, u, i, e and the consonants b, l, p, t, s?
Find the total number of nine-digit numbers that can be formed using the digits 2, 2, 3, 3, 5, 5, 8, 8, 8 so that the odd digits occupy the even places.