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A092467
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a(n)=sum(i+j+k=n,(n+2k)!/i!/j!/(3*k)!) 0<=i,j,k<=n.
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2
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1, 3, 13, 63, 309, 1511, 7373, 35951, 175269, 854455, 4165565, 20307647, 99002389, 482649479, 2352978861, 11471077391, 55922991237, 272631840855, 1329115610269, 6479611111519, 31588945184245, 154000207833639
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OFFSET
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0,2
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COMMENTS
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In general, sum{k=0..n, C(n+2k,3k)*r^k} has g.f. (1-r*x)^2/(1-(3r+1)*x+3r^2*x^2-r^3*x^3). - Paul Barry, Aug 23 2007
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LINKS
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Table of n, a(n) for n=0..21.
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FORMULA
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G.f.: (1-4x+4x^2)/(1-7x+12x^2-8x^3) (conjectured). - R. Stephan, Dec 02 2004
a(n)=sum{k=0..n, C(n+2k,3k)2^(n-k)}; - Paul Barry, Aug 23 2007
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CROSSREFS
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Cf. A007583.
Sequence in context: A122122 A093424 A186242 * A034478 A026715 A001850
Adjacent sequences: A092464 A092465 A092466 * A092468 A092469 A092470
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KEYWORD
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nonn
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AUTHOR
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Benoit Cloitre, Mar 25 2004
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STATUS
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approved
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