import java.math.BigInteger;

public class DUDU {

    public static void main(String[] args) {

        int n = 500;

        for (int i = 5; i <= n; i++) {

            double[][][][] E = new double[2 * n][2 * n + 3][5][4];

            E[0][2][1][0] = 1;

            for (int x = 1; x < 2 * i; x++) {

                for (int s = (x + 1) % 2; s < x + 2; s += 2) {

                    for (int a = 0; a <= 2; a++) {

                        E[x][s + 1][a + 1][0] = E[x - 1][s][a + 1][0] + E[x - 1][s][a + 1][2];

                        E[x][s + 1][a + 1][1] = E[x - 1][s + 2][a + 1][0] + E[x - 1][s + 2][a + 1][1]
                                + E[x - 1][s + 2][a + 1][3];

                        E[x][s + 1][a + 1][2] = E[x - 1][s][a][3] + E[x - 1][s][a + 1][1];

                        E[x][s + 1][a + 1][3] = E[x - 1][s + 2][a + 1][2];
                    }

                }

            }

            BigInteger sum = BigInteger.ZERO;
            double sum1=0;
            
            
            for (int x = 0; x < 4; x++) {
                //System.out.println(E[2 * i - 1][1][3][x]);
               // sum = sum.add(BigInteger.valueOf(E[2 * i - 1][1][3][x]));
                
                sum1+=E[2 * i - 1][1][3][x];
            }
            System.out.println("n=" + i + ": " + sum1);

        }

    }

}