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A128634
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Number of parallel permutations of length n.
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2
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0, 2, 8, 26, 82, 262, 856, 2858, 9722, 33590, 117570, 416022, 1485798, 5348878, 19389688, 70715338, 259289578, 955277398, 3534526378, 13128240838, 48932534038, 182965127278, 686119227298, 2579808294646, 9723892802902, 36734706144302, 139067101832006, 527495903500718
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OFFSET
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1,2
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LINKS
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FORMULA
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a(n) = -2 + 2 * binomial(2*n,n)/(n+1).
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MAPLE
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c:=binomial(2*n, n)/(n+1); seq(2*(c(n)-1), n=1..30); # G. C. Greubel, Dec 02 2019
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MATHEMATICA
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PROG
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(PARI) vector(30, n, 2*(binomial(2*n, n)/(n+1) -1) ) \\ Michel Marcus, Jul 21 2015
(Sage) [2*(catalan_number(n) -1) for n in (1..30)] # G. C. Greubel, Dec 02 2019
(GAP) List([1..30], n-> 2*(Binomial(2*n, n)/(n+1) -1) ); # G. C. Greubel, Dec 02 2019
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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