Code Golf - π day

Programmer Question

The Challenge

The shortest code by character count to display a representation of a circle of radius R using the *character, followed by an approximation of π.

Input is a single number, R.

Since most computers seem to have almost 2:1 ratio you should only output lines where y is odd. This means that when R is odd you should print R-1 lines. There is a new testcase for R=13 to clarify.

eg.

Input
    5
Output      Correct                          Incorrect

        3    *******                    4      *******
        1   *********                   2     *********
       -1   *********                   0    ***********
       -3    *******                   -2     *********
           2.56                        -4      *******
                                            3.44

Edit: Due to widespread confusion caused by odd values of R, any solutions that pass the 4 test cases given below will be accepted

The approximation of π is given by dividing twice the number of * characters by R².

The approximation should be correct to at least 6 significant digits.

Leading or trailing zeros are permitted, so for example any of 3, 3.000000, 003 is accepted for the inputs of 2 and 4.

Code count includes input/output (i.e., full program).

Test Cases

Input
    2
Output
     *** 
     *** 
    3.0

Input
    4
Output
      *****  
     ******* 
     ******* 
      *****  
    3.0

Input
    8
Output
         *******     
      *************  
     *************** 
     *************** 
     *************** 
     *************** 
      *************  
         *******     
    3.125

Input
    10
Output
          *********      
       ***************   
      *****************  
     ******************* 
     ******************* 
     ******************* 
     ******************* 
      *****************  
       ***************   
          *********      
    3.16

Bonus Test Case

Input
    13
Output

           *************       
        *******************    
       *********************   
      ***********************  
     ************************* 
     ************************* 
     ************************* 
     ************************* 
      ***********************  
       *********************   
        *******************    
           *************                                          
    2.98224852071

Find the answer here