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A080473
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a(n)= sum of the products of taking (n-1) numbers from the next n numbers. The next n numbers can be grouped like this (1), (2,3), (4,5,6), (7,8,9,10),... and a(n) is the (sum of the reciprocals of all members) multiplied by (the product of all members).
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1
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1, 5, 74, 2414, 140274, 12780984, 1681732464, 301837526640, 70870658200560, 21085710340560480, 7752245316736838400, 3451176556978487944320, 1829509243576458084345600, 1138750671753488468994278400
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OFFSET
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1,2
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LINKS
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EXAMPLE
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a(3)= 74. The third group of next n numbers is (4,5,6) and a(3) = 4*5 + 5*6+ 4*6= 74.
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CROSSREFS
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KEYWORD
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hard,nonn
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AUTHOR
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EXTENSIONS
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Corrected and extended by Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 06 2003
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STATUS
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approved
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