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Search: id:A022915
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| A022915 |
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Multinomial coefficients(TOP, BOTTOM), where TOP = C(n+1,2), BOTTOM = ( 1 2 3 ... n ). |
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3
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| 1, 1, 3, 60, 12600, 37837800, 2053230379200, 2431106898187968000, 73566121315513295589120000, 65191584694745586153436251091200000, 1906765806522767212441719098019963758016000000, 2048024348726152339387799085049745725891853852479488000000
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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Number of ways to put numbers 1, 2, ..., n*(n+1)/2 in a triangular array of n rows in such a way that each row is increasing. Also number of ways to choose groups of 1, 2, 3, ..., n-1 and n objects out of n*(n+1)/2 objects. - Floor van Lamoen (fvlamoen(AT)hotmail.com), Jul 16 2001
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FORMULA
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a(n) = (n*(n+1)/2)!/(1!*2!*...*n!).
a(n) = a(n-1) * A014068(n) - Dan Fux (dan.fux(AT)OpenGaia.com or danfux(AT)OpenGaia.com), Apr 08 2001.
a(n)=A052295(n)/A000178(n). - Lekraj Beedassy (blekraj(AT)yahoo.com), Feb 19 2004
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CROSSREFS
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Cf. A014068.
Sequence in context: A036770 A006821 A120307 this_sequence A093883 A128075 A106883
Adjacent sequences: A022912 A022913 A022914 this_sequence A022916 A022917 A022918
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KEYWORD
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nonn,easy
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AUTHOR
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Clark Kimberling (ck6(AT)evansville.edu)
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EXTENSIONS
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More terms from Larry Reeves (larryr(AT)acm.org), Apr 11 2001, and from Michel ten Voorde (seqfan(AT)tenvoorde.org) Apr 12 2001
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