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1, 1, 3, 20, 272, 7424, 405504, 44302336, 9680453632, 4230542786560, 3697657604210688, 6463791365183504384, 22598414411798807576576, 158015104883301198495481856, 2209780998563745292895322636288
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,3
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COMMENTS
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a(n+1) is the Hankel transform of A068764.
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LINKS
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FORMULA
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a(n) = 2^C(n,2)*Sum_{k=0..floor(n/2)} C(n,2k)*2^(-k).
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MATHEMATICA
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Table[2^(Binomial[n, 2])*Sum[Binomial[n, 2 k]*2^(-k), {k, 0, Floor[n/2]}], {n, 0, 25}] (* G. C. Greubel, May 07 2016 *)
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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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STATUS
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approved
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