Can someone explain me this question

#1

In a mathematics class, Teacher ask Alice to find the number of all n digit distinct integers which is formed by the two distinct digits ai and bi but there is a rule to form n digit integer.

Rule: She has to form n digit integer by using two digits ai and bi without consecutive bi.

Alice is very weak in maths section. Help her to find the number of such n digit integers.

Input Format:
The first line contains T, the number of test cases. Further T lines contains the value n which is the number of digit in the integer.

Constraints:
1<=T<=40 1<=n<44

Output Format
For each test case print the number of such n digit integer.

Sample Input
3
1
2
3
Sample Output
#1 : 2
#2 : 3
#3 : 5

#2

In this, u have to give 2 recursive calls one for “a” and one for “b” and check that no two “b” come together.

import java.util.Scanner;
import java.util.Arrays;
public class hello{
static int count=0;
public static void classAssignment(int n,String ans){
if(ans.length()==n){
count++;
return;
}
classAssignment(n,ans+“a”);
if(ans.length()==0 || ans.charAt(ans.length()-1)!=‘b’){
classAssignment(n,ans+“b”);
}
}
public static void main(String args[]) {
Scanner scan=new Scanner(System.in);
while(scan.hasNextInt()){
int tc=scan.nextInt();
for(int i=1;i<tc+1;i++){
int n=scan.nextInt();
classAssignment(n,"");
System.out.println("#"+i+" : "+count);
count=0;
}
}
}
}