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A061121
Number of degree-n permutations of order exactly 6.
23
0, 0, 0, 0, 20, 240, 1470, 10640, 83160, 584640, 4496030, 42658440, 371762820, 3594871280, 38650622010, 396457108320, 4330689250160, 53963701424640, 641211774798510, 8205894865096280, 113786291585124060
OFFSET
1,5
FORMULA
E.g.f.: exp(x)-exp(x+1/2*x^2)-exp(x+1/3*x^3)+exp(x+1/2*x^2+1/3*x^3+1/6*x^6).
MATHEMATICA
nn=21; Range[0, nn]!CoefficientList[Series[(Exp[x^6/6]-1)Exp[x+x^2/2+x^3/3]+(Exp[x^2/2]-1)(Exp[x^3/3]-1)Exp[x], {x, 0, nn}], x]//Rest (* Geoffrey Critzer, Feb 04 2013 *)
KEYWORD
easy,nonn
AUTHOR
Vladeta Jovovic, Apr 14 2001
STATUS
approved