Series programs part 2

import java.io.*; 
class series 
{ 
public static void main()throws IOException 
{ 
BufferedReader br=new BufferedReader(new InputStreamReader(System.in)); 
System.out.println("Enter a number of ur choice"); 
int n=Integer.parseInt(br.readLine()); 
int a=1; 
while(a<=n) 
{ 
double b=(int)Math.pow(a,2); 
double c=(int)Math.pow(a,3); 
double num=(int)c-b; 
System.out.print(num+","); 
a++; 
} 
} 
}

import java.io.*; 
class series3 
{ 
public static void main()throws IOException 
{ 
BufferedReader br=new BufferedReader(new InputStreamReader(System.in)); 
System.out.println("Enter a number of ur choice"); 
int n=Integer.parseInt(br.readLine()); 
int sum=0; 
for(int i=1;i<=n;i++) 
{ 
for(int j=1;j<=i;j++) 
{ 
sum+=j; 
} 
} 
System.out.println(sum); 
} 
}

import java.io.*; 
class series5 
{ 
public static void main()throws IOException 
{ 
BufferedReader br=new BufferedReader(new InputStreamReader(System.in)); 
System.out.println("Enter a number of ur choice"); 
int n=Integer.parseInt(br.readLine()); 
int sum=0; 
for(int i=2;i<=n;i++) 
{ 
double sq=Math.pow(i,2); 
sum+=sq; 
} 
System.out.println(sum); 
} 
}