b21 := (1,3,6)(2,4,8)(5,9,14)(7,11,17)(10,15,21)(12,18,25)(16,22,30)(19,26,33)
     (20,27,35)(23,31,40)(24,32,42)(28,36,47)(29,37,48)(34,44,56)(38,49,61)
     (39,50,63)(41,52,66)(43,54,55)(45,57,71)(46,58,73)(51,64,65)(53,67,81)
     (59,74,85)(60,75,88)(62,77,91)(68,82,97)(69,83,99)(70,84,87)(72,86,101)
     (76,89,90)(78,92,106)(79,93,108)(80,94,109)(95,110,96)(98,112,125)(100,
     114,128)(102,115,129)(103,116,131)(104,117,133)(105,118,135)(107,120,138)
     (111,123,142)(113,126,127)(119,136,137)(121,139,155)(122,140,157)(124,
     143,159)(130,147,163)(132,149,166)(134,151,169)(141,158,177)(144,160,180)
     (146,161,162)(148,164,183)(150,167,168)(152,170,188)(153,171,190)(154,
     172,192)(156,174,195)(165,184,202)(173,193,194)(175,196,210)(176,197,211)
     (178,198,212)(179,199,213)(181,200,214)(182,201,215)(185,203,218)(186,
     204,187)(189,206,221)(191,207,222)(205,219,230)(208,223,235)(209,224,236)
     (216,227,240)(217,228,242)(220,231,244)(225,237,249)(226,238,251)(229,
     243,257)(232,245,260)(233,239,252)(234,246,262)(241,254,258)(247,263,248)
     (250,264,274)(253,267,268)(255,269,256)(261,271,273)(265,275,266)(270,
     277,276)(278,279,280);