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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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%I #2 Dec 05 2013 19:56:00
%S 1,5,74,2414,140274,12780984,1681732464,301837526640,70870658200560,
%T 21085710340560480,7752245316736838400,3451176556978487944320,
%U 1829509243576458084345600,1138750671753488468994278400
%N 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).
%e a(3)= 74. The third group of next n numbers is (4,5,6) and a(3) = 4*5 + 5*6+ 4*6= 74.
%Y Cf. A080474.
%K hard,nonn
%O 1,2
%A _Amarnath Murthy_, Mar 11 2003
%E Corrected and extended by Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 06 2003
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