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A195210
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Sum of odd divisors of !n.
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4
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1, 0, 1, 1, 13, 12, 324, 1352, 18368, 19152, 1994322, 8810748, 193690826, 829046868, 34563283272, 274895151856, 14554448767872, 8178592487376, 2493850026398472, 33842416675133248, 1037660717168380800, 6072370562498569056, 682597834324732589120, 5390950170768906240000
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OFFSET
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0,5
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COMMENTS
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!n is a subfactorial number (A000166).
Property of the sequence: for n > 4 the sum of odd divisors of !n seems even.
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LINKS
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FORMULA
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EXAMPLE
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a(7) = 1352 because the divisors of !7 = 1854 are {1, 2, 3, 6, 9, 18, 103, 206, 309, 618, 927, 1854}, and the sum of the 6 odd divisors 1, 3, 9, 103, 309 and 927 is 1352.
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MATHEMATICA
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Table[Total[Select[Divisors[Subfactorial[n]], OddQ[ # ]&]], {n, 0, 21}]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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