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Search: id:A049612
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| 0, 1, 5, 19, 63, 192, 552, 1520, 4048, 10496, 26624, 66304, 162560, 393216, 940032, 2224128, 5214208, 12124160, 27983872, 64159744, 146210816, 331350016, 747110400, 1676673024, 3746562048, 8338276352, 18488492032
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OFFSET
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0,3
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COMMENT
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If X_1,X_2,...,X_n are 2-blocks of a (2n+3)-set X then, for n>=1, a(n+1) is the number of (n+3)-subsets of X intersecting each X_i, (i=1,2,...,n). - Milan R. Janjic (agnus(AT)blic.net), Nov 18 2007
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LINKS
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Milan Janjic, Two Enumerative Functions
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FORMULA
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G.f.: (x*(1-x)^3)/(1-2*x)^4.
a(n)=sum{k=0..floor((n+3)/2), C(n+3, 2k)C(k+1, 3) } - Paul Barry (pbarry(AT)wit.ie), May 15 2003
a(n+1)=1/48*2^n*n^3+5/16*2^n*n^2+7/6*2^n*n+2^n, n=1,2,... - Milan R. Janjic (agnus(AT)blic.net), Nov 18 2007
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CROSSREFS
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Row sums of triangle A055252. a(n+1)= A055584(n, 0), n >= 0.
Sequence in context: A036677 A003296 A053545 this_sequence A001870 A025568 A001047
Adjacent sequences: A049609 A049610 A049611 this_sequence A049613 A049614 A049615
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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)
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