A prime circle of order 
 is a free circular permutation of the numbers
 from 1 to 
 with adjacent pairs summing to a prime.
 The number of prime circles for 
, 2, ..., are 1, 1, 1, 2, 48, 512, ... (OEIS A051252).
 The prime circles for the first few even orders are given in the table below.
| prime circles | |
| 2 | |
| 4 | |
| 6 | |
| 8 | 
 
         
	    
	
    
