A080473 - OEIS

A080473

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).

1, 5, 74, 2414, 140274, 12780984, 1681732464, 301837526640, 70870658200560, 21085710340560480, 7752245316736838400, 3451176556978487944320, 1829509243576458084345600, 1138750671753488468994278400

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..14.

EXAMPLE

a(3)= 74. The third group of next n numbers is (4,5,6) and a(3) = 4*5 + 5*6+ 4*6= 74.

CROSSREFS

Cf. A080474.

Sequence in context: A251666 A192564 A374980 * A266570 A355121 A376112

Adjacent sequences: A080470 A080471 A080472 * A080474 A080475 A080476

KEYWORD

hard,nonn

AUTHOR

Amarnath Murthy, Mar 11 2003

EXTENSIONS

Corrected and extended by Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 06 2003

STATUS

approved