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A069660
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Order of the subgroup of the symmetric group S_n generated by the cycles (1,3) and (1,2,3,...,n).
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0
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6, 8, 120, 72, 5040, 1152, 362880, 28800, 39916800, 1036800, 6227020800, 50803200, 1307674368000, 3251404800, 355687428096000, 263363788800, 121645100408832000, 26336378880000, 51090942171709440000
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OFFSET
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3,1
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LINKS
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FORMULA
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If n is odd a(n) = n!, if n is even a(n) = 2 * ((n/2)!)^2 = 2 * n! / A000984(n/2) = 2 * A001044(n/2).
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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Sharon Sela (sharonsela(AT)hotmail.com), May 16 2002
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EXTENSIONS
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STATUS
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approved
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