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Search: id:A086405
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| 1, 4, 18, 84, 396, 1872, 8856, 41904, 198288, 938304, 4440096, 21010752, 99423936, 470479104, 2226331008, 10535111424, 49852682496, 235905426432, 1116316463616, 5282466223104, 24996898556928, 118286594002944
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Binomial transform of A079935.
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FORMULA
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G.f.: (1-2x)/((1-(3-sqrt(3))x)(1-(3+sqrt(3))x))=(1-2x)/(1-6x+6x^2); a(n)=(3-sqrt(3))^n(1/2-1/(2sqrt(3)))+(3+sqrt(3))^n(1/2+1/(2sqrt(3))).
E.g.f. : exp(3x)(cosh(sqrt(3x)+sinh(sqrt(3)x)/sqrt(3)) - Paul Barry (pbarry(AT)wit.ie), Nov 20 2003
a(n)=sum{k=1..floor(n/2), C(n, 2k)3^(n-k-1)} - Paul Barry (pbarry(AT)wit.ie), Nov 22 2003
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CROSSREFS
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Sequence in context: A143646 A014348 A126020 this_sequence A151251 A010849 A007859
Adjacent sequences: A086402 A086403 A086404 this_sequence A086406 A086407 A086408
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KEYWORD
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easy,nonn
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Jul 19 2003
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