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A026033
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C(4n,n) - C(4n,n-4).
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0
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1, 4, 28, 220, 1819, 15484, 134320, 1180764, 10482340, 93766288, 843822148, 7631018564, 69291185474, 631334484200, 5769124912320, 52851389067420, 485242722376524, 4463782855666480, 41133265444555120
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OFFSET
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0,2
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LINKS
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FORMULA
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G.f.: (g-2)*(2-2*g+g^2)*g^2/(3*g-4) where g = 1+x*g^4 is the g.f. of A002293. - Mark van Hoeij, Nov 11 2011
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CROSSREFS
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a(n) = T(4n, n), where T is defined in A026022.
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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