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Search: id:A025035
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| A025035 |
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Number of partitions of { 1, 2, ..., 3n } into sets of size 3. |
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+0
10
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| 1, 1, 10, 280, 15400, 1401400, 190590400, 36212176000, 9161680528000, 2977546171600000, 1208883745669600000, 599606337852121600000, 356765771022012352000000, 250806337028474683456000000
(list; graph; listen)
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OFFSET
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0,3
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FORMULA
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(3n)!/(n!(3!)^n). (Christian G. Bower bowerc(AT)usa.net 9/1998).
Integral representation as n-th moment of a positive function on the positive axis, in Maple notation: int(x^n*sqrt(2/(3*x))*BesselK(1/3, 2*sqrt(2*x)/3)/Pi, x=0..infinity), n=0, 1... . Karol A. Penson (penson(AT)lptl.jussieu.fr), Oct 05 2005.
E.g.f.: exp(x^3/3!) (with interpolated zeros) - Paul Barry (pbarry(AT)wit.ie), May 26 2003
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PROGRAM
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(PARI) a(n)=if(n<0, 0, (3*n)!/n!/6^n)
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CROSSREFS
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Sequence in context: A055055 A117654 A067427 this_sequence A012243 A077281 A049387
Adjacent sequences: A025032 A025033 A025034 this_sequence A025036 A025037 A025038
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KEYWORD
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nonn
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AUTHOR
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David W. Wilson (davidwwilson(AT)comcast.net)
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