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Search: id:A055799
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| 1, 8, 37, 130, 385, 1012, 2431, 5434, 11440, 22880, 43758, 80444, 142766, 245480, 410210, 667964, 1062347, 1653608, 2523675, 3782350, 5574855, 8090940, 11575785, 16342950, 22789650, 31414656, 42839148, 57830872
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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If Y is a 2-subset of an n-set X then, for n>=9, a(n-9) is the number of 9-subsets of X which have no exactly one element in common with Y. - Milan R. Janjic (agnus(AT)blic.net), Dec 28 2007
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FORMULA
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a(n-9)=binomial(n,9)-2*binomial(n-2,8), n=9,10,.... - Milan R. Janjic (agnus(AT)blic.net), Dec 28 2007
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MATHEMATICA
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a=1; b=2; c=3; d=4; e=5; f=6; g=7; s=8; lst={1, s}; Do[a+=n; b+=a; c+=b; d+=c; e+=d; f+=e; g+=f; s+=g; AppendTo[lst, s], {n, 6!}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), May 24 2009]
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CROSSREFS
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Sequence in context: A052387 A001780 A053296 this_sequence A035038 A111645 A128246
Adjacent sequences: A055796 A055797 A055798 this_sequence A055800 A055801 A055802
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KEYWORD
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nonn
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AUTHOR
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Clark Kimberling (ck6(AT)evansville.edu), May 28 2000
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