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A056923
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Write the integers in groups: 0; 1,2; 3,4,5; 6,7,8,9; ... and form the product of the members of each group.
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0
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0, 2, 60, 3024, 240240, 27907200, 4475671200, 948964262400, 257256702743040, 86839771951296000, 35728290125079552000, 17602963463032472448000, 10233395250958706770944000, 6932022668773077815267328000
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OFFSET
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0,2
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COMMENTS
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Each group begins with a triangular number and proceeds until one short of the next triangular number.
Also, the number under the radical using Brahmagupta's formula for a n-sided cyclic quadrilateral with sides 1..n - Ben Thurston (benthurston27(AT)yahoo.com), Dec 05 2006
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LINKS
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Table of n, a(n) for n=0..13.
Nick's Mathematical Puzzles, Problem p10
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FORMULA
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(n (n + 3)/2)!/((n - 1)(n + 2)/2)!
(s-1)*(s-2)*...*(s-n) where s is the sum(n, n=0..i) - Ben Thurston (benthurston27(AT)yahoo.com), Dec 05 2006
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MAPLE
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m:=1; for i from 1 to 10 do m:=1; for j from 1 to i do m:= m*(sum(k, k = 0..i)-j); end do; print(m); end do; - Ben Thurston (benthurston27(AT)yahoo.com), Dec 05 2006
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MATHEMATICA
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Table[(n (n + 3)/2)!/((n - 1)(n + 2)/2)!, {n, 0, 15}]
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CROSSREFS
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Cf. A027480.
Sequence in context: A157059 A222652 A199643 * A173221 A082787 A078423
Adjacent sequences: A056920 A056921 A056922 * A056924 A056925 A056926
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KEYWORD
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nonn
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AUTHOR
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Robert G. Wilson v, Sep 09 2000
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STATUS
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approved
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