Sum of squares
Public static void main (String [] args) throws IOException {int n; String s; BufferedReader buf; buf = new BufferedReader (new InputStreamReader (System. in); System. out. print ("enter a natural number:"); s = buf. readLine (); n = Integer. parseInt (s); System. out. print ("f (n) = 1"); for (int I = 2; I <= n; I ++) System. out. print ("+" + I * I); System. out. print ("=" + Square (n);} public static long Square (int n) {long f = 0; if (n <0) System. out. println ("n <0, input error Incorrect! "); Else if (n = 1) f = 1; else f = Square (n-1) + n * n; return f ;}
Exhaustive quantity
public static void main(String args[]){int i,j;for(j=2;;j++) {for(i=2;i<=j/2;i++) {if(j%i==0)break;}if(i>j/2) {System.out.println(j);}}}
Quality Factor
Public static void main (String [] args) {int n = 0; String s = null; BufferedReader buf; buf = new BufferedReader (new InputStreamReader (System. in); System. out. print ("enter a number:"); try {s = buf. readLine ();} catch (IOException e) {e. printStackTrace ();} n = Integer. parseInt (s); int temp = n; for (int I = 2; I <= temp; I ++) {if (! IsPrime (I) {continue;} while (true) {if (temp % I = 0) {temp = temp/I; System. out. println (I) ;}else {break ;}}} public static boolean isPrime (int n) {int I; for (I = 2; I <= n; I ++) {if (n % I = 0) {break ;}} if (I >=n) {return true ;} else {return false ;}}