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Search: id:A027777
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| 6, 40, 150, 420, 980, 2016, 3780, 6600, 10890, 17160, 26026, 38220, 54600, 76160, 104040, 139536, 184110, 239400, 307230, 389620, 488796, 607200, 747500, 912600, 1105650, 1330056, 1589490, 1887900, 2229520, 2618880
(list; graph; listen)
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OFFSET
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0,1
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FORMULA
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Number of 7-subsequences of [ 1, n ] with just 2 contiguous pairs; g.f. 2*(3+2x)/(1-x)^6.
C(n+3, 3)*C(n+4, 2) - Zerinvary Lajos (zlaja(AT)freemail.hu), May 13 2005
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MAPLE
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[seq (stirling2(n+1, n)*binomial(n, 3), n=3..32)]; - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 05 2006
a:=n->(sum((numbperm(n, 4)), j=2..n)):seq(a(n)/12, n=4..33); # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Aug 26 2008]
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CROSSREFS
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Twice A006411.
Contribution from Johannes W. Meijer (meijgia(AT)hotmail.com), Oct 16 2009: (Start)
Equals second right hand column of A163934.
(End)
Sequence in context: A114079 A002595 A089207 this_sequence A073773 A001919 A005553
Adjacent sequences: A027774 A027775 A027776 this_sequence A027778 A027779 A027780
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KEYWORD
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nonn
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AUTHOR
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thi ngoc dinh (via rkg(AT)cpsc.ucalgary.ca)
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