Codigo de cuadrados

Codigo que si me sale
package cuadrados.medios;
import javax.swing.*;
public class Cuadrados extends javax.swing.JFrame {

public Cuadrados() {
initComponents();
}@SuppressWarnings("unchecked")
//
private void initComponents() {

jPanel1 = new javax.swing.JPanel();
jLabel1 = new javax.swing.JLabel();
jPanel2 = newjavax.swing.JPanel();
jLabel2 = new javax.swing.JLabel();
txt_Semilla = new javax.swing.JTextField();
jLabel3 = new javax.swing.JLabel();
txt_Numero = newjavax.swing.JTextField();
btn_Generar = new javax.swing.JButton();
jScrollPane1 = new javax.swing.JScrollPane();
lst_Numeros = new javax.swing.JTextArea();
jLabel4 = newjavax.swing.JLabel();

setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

jPanel1.setBackground(new java.awt.Color(255, 255, 204));jPanel1.setBorder(javax.swing.BorderFactory.createLineBorder(new java.awt.Color(255, 255, 0)));

jLabel1.setFont(new java.awt.Font("Chiller", 0, 24)); // NOI18N
jLabel1.setForeground(new java.awt.Color(255, 0,0));
jLabel1.setText("Cuadrados Medios");

jPanel2.setBackground(new java.awt.Color(204, 255, 204));
jPanel2.setBorder(javax.swing.BorderFactory.createLineBorder(newjava.awt.Color(51, 255, 0)));

jLabel2.setFont(new java.awt.Font("Chiller", 0, 18)); // NOI18N
jLabel2.setText("Semilla:");

txt_Semilla.setFont(new java.awt.Font("Chiller", 0,18)); // NOI18N
txt_Semilla.setForeground(new java.awt.Color(0, 0, 255));

jLabel3.setFont(new java.awt.Font("Chiller", 0, 18)); // NOI18N
jLabel3.setText("Numeros agenerar:");

txt_Numero.setFont(new java.awt.Font("Chiller", 0, 18)); // NOI18N
txt_Numero.setForeground(new java.awt.Color(0, 0, 255));

btn_Generar.setBackground(new...