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Search: id:A050486
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| 1, 9, 44, 156, 450, 1122, 2508, 5148, 9867, 17875, 30888, 51272, 82212, 127908, 193800, 286824, 415701, 591261, 826804, 1138500, 1545830, 2072070, 2744820, 3596580, 4665375, 5995431, 7637904, 9651664, 12104136, 15072200, 18643152
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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If a 2-set Y and an (n-3)-set Z are disjoint subsets of an n-set X then a(n-8) is the number of 8-subsets of X intersecting both Y and Z. - Milan R. Janjic (agnus(AT)blic.net), Sep 08 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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LINKS
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Milan Janjic, Two Enumerative Functions
Matthew M. Conroy, Home page (listed instead of email address)
Index entries for sequences related to Chebyshev polynomials.
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FORMULA
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a(n)= ((-1)^n)*A053120(2*n+7, 7)/64 (1/64 of eighth unsigned column of Chebyshev T-triangle, zeros omitted).
G.f.: (1+x)/(1-x)^8.
a(n)=2*C(n+7, 7)-C(n+6, 6). - Paul Barry (pbarry(AT)wit.ie), Mar 04 2003
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CROSSREFS
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Partial sums of A040977.
Adjacent sequences: A050483 A050484 A050485 this_sequence A050487 A050488 A050489
Sequence in context: A110125 A034194 A075206 this_sequence A036599 A059825 A074631
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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 Matthew M. Conroy, May 23 2001
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