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Search: id:A050494
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| 1, 10, 52, 192, 570, 1452, 3300, 6864, 13299, 24310, 42328, 70720, 114036, 178296, 271320, 403104, 586245, 836418, 1172908, 1619200, 2203630, 2960100, 3928860, 5157360, 6701175, 8625006, 11003760, 13923712, 17483752, 21796720, 26990832
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OFFSET
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0,2
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COMMENT
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If Y is a 3-subset of an n-set X then, for n>=9, a(n-9) is the number of 9-subsets of X having at least two elements in common with Y. - Milan R. Janjic (agnus(AT)blic.net), Nov 23 2007
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REFERENCES
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A. H. Beiler, Recreations in the Theory of Numbers, Dover, N.Y., 1964, pp. 194-196.
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FORMULA
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a(n)=C(n+6, 6)*(3n+7)/7.
G.f.: (1+2*x)/(1-x)^8.
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CROSSREFS
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Cf. A051923.
Cf. A093560 ((3, 1) Pascal, column m=7).
Sequence in context: A058827 A028994 A092966 this_sequence A119543 A063899 A006889
Adjacent sequences: A050491 A050492 A050493 this_sequence A050495 A050496 A050497
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KEYWORD
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easy,nonn
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AUTHOR
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Barry E. Williams, Dec 26 1999
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EXTENSIONS
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More terms from Antonio G. Astudillo (afg_astudillo(AT)hotmail.com), Jun 17 2001
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