若一头母牛,从出生起第四年开始每年生一头牛,按此规律,第N年时有多少头母牛?撇开实际问题,当它生出来的全是母牛,并且都在四年后开始每年生一头母牛

Question

若一头母牛,从出生起第四年开始每年生一头牛,按此规律,第N年时有多少头母牛?
撇开实际问题,当它生出来的全是母牛,并且都在四年后开始每年生一头母牛

Answer 1

用VB编程如下:
Private Sub Command1_Click()
Dim str1 As String
Dim n As Integer
Dim Qty As Long
While n = 0
str1 = InputBox("第N年?","请输入一整数")
n = Val(str1)
Wend
Qty = 1
While n >= 4
Qty = Qty + (n - 3)
n = n - 3
Wend
MsgBox Qty
End Sub