Mi sono imbattuto in questo problema, 
  There is a particular sequence only uses the numbers 1, 2, 3, 4 and no two adjacent numbers are the same.
  Write a program that given n1 1s, n2 2s, n3 3s, n4 4s will output the number of such sequences...                            
                                                        
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                                 09.11.2014 - 09:24