a21 := (1,3,6,11,18,29,45)(2,4,8,14,22,36,55)(5,9,16,25,40,61,90)(7,12,20,32,
     49,74,44)(10,17,27,42,65,95,132)(13,21,34,52,78,110,154)(15,23,37,57,84,
     117,112)(19,30,46,69,101,141,189)(24,38,58,85,119,164,211)(26,41,63,92,
     127,174,221)(28,43,67,98,136,183,173)(31,47,71,103,60,88,122)(33,50,75,
     107,149,197,243)(35,53,79,111,128,175,218)(39,59,87,121,168,215,260)(48,
     72,104,64,93,129,176)(51,76,68,99,138,185,231)(54,80,113,156,203,251,293)
     (56,82,106,147,150,198,245)(62,91,125,171,219,264,301)(66,96,134,181,228,
     272,257)(70,102,143,83,115,159,207)(73,105,146,193,240,282,313)(77,108,
     151,199,247,289,285)(81,114,158,205,253,294,153)(86,120,166,214,223,268,
     304)(89,123,133,180,227,271,307)(94,130,177,224,269,305,167)(97,135,182,
     229,131,178,157)(100,139,186,232,275,118,162)(109,152,200,248,290,225,
     137)(116,160,208,226,270,306,331)(124,170,217,263,299,209,256)(126,172,
     220,266,302,328,336)(140,187,233,244,286,316,338)(142,190,236,277,311,
     334,354)(144,191,238,280,287,317,235)(145,192,239,281,259,297,323)(148,
     195,241,284,315,234,276)(155,202,250,165,212,188,179)(161,201,249,291,
     319,339,356)(163,210,194,184,230,273,309)(169,204,252,216,261,196,242)
     (206,254,295,321,343,349,265)(213,258,262,298,325,347,359)(222,267,303,
     329,351,361,363)(237,278,312,308,332,352,330)(246,288,318,326,348,342,
     357)(255,296,322,344,292,320,341)(274,310,333,353,283,314,337)(279,300,
     327,350,360,362,364)(324,345,346,358,340,335,355);