a21 := (1,2,4,7,11)(3,5,9,13,18)(6,10,14,20,26)(8,12,16,23,29)(15,21,27,33,39)
     (17,24,31,37,44)(19,25,32,38,45)(22,28,35,41,48)(30,36,43,50,58)(34,40,
     47,53,63)(42,49,56,67,82)(46,52,61,73,87)(51,59,71,86,102)(54,64,77,92,
     70)(55,65,79,95,110)(57,68,84,100,116)(60,72,76,91,107)(62,74,89,104,120)
     (66,80,97,112,126)(69,85,101,117,131)(75,90,105,121,133)(78,93,108,123,
     135)(81,98,113,127,138)(83,99,115,129,141)(88,96,111,125,137)(94,109,124,
     136,146)(103,119,132,144,143)(106,122,134,145,147)(114,128,139,149,118)
     (130,142,150,148,140)(151,152,153,154,155);