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A081202
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8th binomial transform of (0,1,0,1,0,1,....), A000035.
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8
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0, 1, 16, 193, 2080, 21121, 206896, 1979713, 18640960, 173533441, 1602154576, 14701866433, 134294124640, 1222488408961, 11099284691056, 100571785292353, 909893629141120, 8222275592839681, 74233110849544336, 669726411243809473
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OFFSET
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0,3
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COMMENTS
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For a combinatorial interpretation of a(n) with special 9-letter words of length n see the comment in A081200 on the 7-letter analog.
The binomial transform of {a(n)}_{n >=0} is A081203, the 10-letter analog.
(End)
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LINKS
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FORMULA
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a(n) = 16a(n-1)-63a(n-2), a(0)=0, a(1)=1.
G.f.: x/((1-7*x)*(1-9*x)).
a(n) = (9^n - 7^n)/2.
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MATHEMATICA
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CoefficientList[Series[x / ((1 - 7 x) (1 - 9 x)), {x, 0, 20}], x] (* Vincenzo Librandi, Aug 07 2013 *)
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PROG
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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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