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A109957
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Diagonal sums of number triangle A109956.
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1
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1, -1, 4, -16, 74, -368, 1926, -10455, 58333, -332489, 1927761, -11334128, 67416570, -404956315, 2453012916, -14967587873, 91910798556, -567566697627, 3522334450512, -21957276973619, 137425078658354, -863229921626723, 5440215989173113, -34388244134246836
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OFFSET
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0,3
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LINKS
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FORMULA
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G.f. : g/(1-f) where f/(1-f)^3=x and g=1-f; a(n)=(-1)^n*sum{k=0..floor(n/2), ((3k+1)/(2n-k+1))*binomial(3n-3k, n-2k)}.
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CROSSREFS
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KEYWORD
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easy,sign
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AUTHOR
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STATUS
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approved
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