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Search: id:A055796
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| 1, 5, 16, 42, 98, 210, 420, 792, 1419, 2431, 4004, 6370, 9828, 14756, 21624, 31008, 43605, 60249, 81928, 109802, 145222, 189750, 245180, 313560, 397215, 498771, 621180, 767746, 942152
(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>=6, a(n-6) is the number of 6-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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LINKS
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Alexsandar Petojevic, The Function vM_m(s; a; z) and Some Well-Known Sequences, Journal of Integer Sequences, Vol. 5 (2002), Article 02.1.7
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FORMULA
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(n+1)(n+2)(n+3)(n+4)(n^2-n+30)/720.
binomial(n,6)+binomial(n,4),n>=4. - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jul 24 2006
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MAPLE
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[seq(binomial(n, 6)+binomial(n, 4), n=4..33)]; - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jul 24 2006
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MATHEMATICA
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a=1; b=2; c=3; d=4; s=5; lst={1, s}; Do[a+=n; b+=a; c+=b; d+=c; s+=d; 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: A014171 A014175 A097810 this_sequence A002662 A143962 A066634
Adjacent sequences: A055793 A055794 A055795 this_sequence A055797 A055798 A055799
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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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