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A127847
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a(n)=4^C(n,2)*(4^n-1)/3.
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1
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0, 1, 20, 1344, 348160, 357564416, 1465657589760, 24017731997138944, 1574098141758535761920, 412645105639632468417970176, 432690992231222540584116394393600, 1814838857553600260569028862094736359424, 30447948962887853884238295543591323273401466880
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OFFSET
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0,3
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COMMENTS
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-a(n) is the Hankel transform of A127846, the series reversion of x/(1+5x+4x^2). Note that (4^n-1)/3 has g.f. x/(1-5x+4x^2).
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LINKS
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MATHEMATICA
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Table[4^Binomial[n, 2] (4^n-1)/3, {n, 0, 20}] (* Harvey P. Dale, Aug 29 2015 *)
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CROSSREFS
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KEYWORD
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easy,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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