母牛生小牛问题

若母牛从其出生第四年（3周年后）开始每年都会生一头小母牛，按这个规律，1头年龄为year的母牛在futureYear个年头后会生几头母牛？

C# Code:

class Cow

{

static void Main(string[] args)

{

for (int i = 0; i <= 10; i++)

{

Console.WriteLine(new Cow(0, i).SonNumber.ToString());

}

Console.ReadKey();

}

public Cow(int year, int futureYear)

{

this.year = year;

this.futureYear = futureYear;

CountSonNumber();

}

private int year;

private int futureYear;

public int SonNumber { get; private set; }

private void CountSonNumber()

{

var leftYears = futureYear;

var currentYear = year;

SonNumber = 1;

while (currentYear < 3)

{

if (leftYears > 0)

{

currentYear++;

leftYears--;

}

else

{

return;

}

}

for (int i = 0; i <= leftYears; i++)

{

Cow newCow = new Cow(0,leftYears-i);

SonNumber += newCow.SonNumber;

}

}

}

Output:

1

1

1

2

3

4

6

9

13

19

28