b21 := (1,3,6,8,12)(2,4,5,7,10)(9,13,16,21,28)(11,15,19,25,34)(14,17,22,30,39)
     (18,23,31,40,50)(20,26,36,45,56)(24,32,42,52,63)(27,37,47,57,68)(29,38,
     49,60,46)(33,43,53,64,75)(35,44,55,66,54)(41,51,62,74,88)(48,58,70,82,77)
     (59,71,84,99,115)(61,72,86,101,116)(65,76,91,107,79)(67,78,93,109,125)
     (69,80,94,110,73)(81,95,106,121,140)(83,97,113,131,149)(87,102,117,135,
     134)(89,104,119,126,100)(90,105,120,139,155)(92,108,123,142,137)(96,111,
     128,146,162)(98,114,133,151,158)(103,118,136,153,167)(112,129,147,163,
     127)(122,141,157,152,166)(124,143,145,160,164)(130,148,144,159,170)(132,
     150,165,172,175)(138,154,168,161,171)(156,169,173,174,176);