public class Solution
extends Object
1641 - Count Sorted Vowel Strings\.
Medium
Given an integer `n`, return _the number of strings of length_ `n` _that consist only of vowels (_`a`_,_ `e`_,_ `i`_,_ `o`_,_ `u`_) and are **lexicographically sorted**._
A string `s` is **lexicographically sorted** if for all valid `i`, `s[i]` is the same as or comes before `s[i+1]` in the alphabet.
**Example 1:**
**Input:** n = 1
**Output:** 5
**Explanation:** The 5 sorted strings that consist of vowels only are `["a","e","i","o","u"].`
**Example 2:**
**Input:** n = 2
**Output:** 15
**Explanation:** The 15 sorted strings that consist of vowels only are
["aa","ae","ai","ao","au","ee","ei","eo","eu","ii","io","iu","oo","ou","uu"].
Note that "ea" is not a valid string since 'e' comes after 'a' in the alphabet.
**Example 3:**
**Input:** n = 33
**Output:** 66045
**Constraints:**
* `1 <= n <= 50`