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Search: id:A098469
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| A098469 |
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A sequence related to the even-indexed Catalan numbers. |
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+0
1
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| 1, 2, 6, 20, 78, 332, 1516, 7240, 35734, 180620, 929940, 4858328, 25687052, 137177016, 738819672, 4008435984, 21886788582, 120178329740, 663179894788, 3675923244856, 20456707469540, 114254175491304, 640223315385576
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Binomial transform of A098465. Second binomial transform of (1,0,2,0,14,0,132,0,1430,..) (Set odd-indexed Catalan numbers to zero).
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FORMULA
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G.f.: (sqrt(1+2x)-sqrt(1-6x))/(4x*sqrt(1-2x))
a(n)=sum{k=0..floor(n/2), C(n,2k)*C(k)*2^(n-2k)}; a(n)=sum{k=0..n, c(n,k)*2^(n-k)*C(k)*(1-(-1)^k)/2};
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CROSSREFS
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Cf. A048990.
Adjacent sequences: A098466 A098467 A098468 this_sequence A098470 A098471 A098472
Sequence in context: A083691 A000898 A027215 this_sequence A081563 A038393 A027221
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KEYWORD
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easy,nonn
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Sep 09 2004, corrected Mar 31 2007
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