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Search: id:A098746
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| A098746 |
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Number of permutations of [1..n] which avoid 4231 and 42513. |
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+0
4
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| 1, 1, 2, 6, 23, 102, 495, 2549, 13682, 75714, 428882, 2474573, 14492346, 85926361, 514763279, 3111119358, 18946375767, 116147683902, 716179441293, 4438862153246, 27638747494178, 172805469880497, 1084462349973559, 6828717036765622, 43132158190994223, 273204023401012901
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OFFSET
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0,3
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REFERENCES
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M. H. Albert et al., Restricted permutations and queue junping, Discrete Math., 287 (2004), 129-133.
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FORMULA
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G.f.: 1+Sum( t^n * Sum( (n-l)*binomial(2*l+n, l)/(2*l+n), l=0..n ), n=1..oo).
G.f.: sqrt(3)/(sqrt(3)-2*sqrt(x)*sin(asin(3*sqrt(3x)/2)/3)); - Paul Barry (pbarry(AT)wit.ie), Dec 15 2006
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MAPLE
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1+add( t^n * add( (n-l)*binomial(2*l+n, l)/(2*l+n), l=0..n ), n=1..30);
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CROSSREFS
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Adjacent sequences: A098743 A098744 A098745 this_sequence A098747 A098748 A098749
Sequence in context: A078487 A120346 A050389 this_sequence A088929 A004040 A022558
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KEYWORD
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nonn
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AUTHOR
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njas, Oct 30 2004
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