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Search: id:A029651
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| 1, 3, 9, 30, 105, 378, 1386, 5148, 19305, 72930, 277134, 1058148, 4056234, 15600900, 60174900, 232676280, 901620585, 3500409330, 13612702950, 53017895700, 206769793230, 807386811660, 3156148445580, 12350146091400, 48371405524650
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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If Y is a fixed 2-subset of a (2n+1)-set X then a(n) is the number of (n+1)-subsets of X intersecting Y. - Milan R. Janjic (agnus(AT)blic.net), Oct 28 2007
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LINKS
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Milan Janjic, Two Enumerative Functions
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FORMULA
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a(n)= 3 * binomial(2n-1, n) (n>0). - Len Smiley (smiley(AT)math.uaa.alaska.edu), Nov 03 2001
G.f.: (1+xC(x))/(1-2xC(x)), C(x) the g.f. of A000108. - Paul Barry (pbarry(AT)wit.ie), Dec 17 2004
a(n)=A003409(n), n>0. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 23 2008]
a(n)=Sum_{k, 0<=k<=n} A039599(n,k)*A000034(k). [From Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Oct 29 2008]
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CROSSREFS
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a(n)/3 = A001700(n-1), (n>1)
Sequence in context: A145268 A148956 A003409 this_sequence A148957 A148958 A024332
Adjacent sequences: A029648 A029649 A029650 this_sequence A029652 A029653 A029654
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KEYWORD
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nonn
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AUTHOR
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Mohammad K. Azarian (ma3(AT)evansville.edu)
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EXTENSIONS
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More terms from David W. Wilson (davidwwilson(AT)comcast.net)
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