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A078718
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Let f(i,j) = Sum(binomial(2*i,k)*binomial(2*j,i+j-k)*(-1)^(i+j-k),k=0..2*i) (this is essentially the same as the triangle in A068555); then a(n) = f(n,n-2)/2.
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1
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0, 1, 3, -5, 14, -45, 154, -546, 1980, -7293, 27170, -102102, 386308, -1469650, 5616324, -21544100, 82907640, -319929885, 1237518450, -4796857230, 18627909300, -72457790790, 282257178060, -1100982015900, 4299680491080, -16809921068850, 65785111513524, -257683159276956
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OFFSET
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0,3
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LINKS
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Table of n, a(n) for n=0..27.
Guo-Niu Han, Enumeration of Standard Puzzles
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CROSSREFS
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Cf. A068555. Apart perhaps from signs, f(n, 0) and f(n, n) give A000984, f(n, 1) gives A002420, f(n, n-1) gives 2*A000984.
Sequence in context: A222380 A052974 A006395 * A081393 A129326 A167553
Adjacent sequences: A078715 A078716 A078717 * A078719 A078720 A078721
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KEYWORD
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sign
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AUTHOR
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N. J. A. Sloane, Dec 20 2002
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STATUS
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approved
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