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0, 5, 45, 335, 2385, 16775, 117585, 823415, 5764545, 40353095, 282474225, 1977324695, 13841283105, 96889002215, 678223056465, 4747561477175, 33232930504065, 232630513856135, 1628413597648305, 11398895184848855
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,2
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COMMENTS
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Length-n words from letters {1,2,...,7} with at least one letter >2. [Joerg Arndt, Jun 02 2011]
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LINKS
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FORMULA
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a(n) = 9*a(n-1) - 14*a(n-2).
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MATHEMATICA
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CoefficientList[Series[5 x/((1 - 2 x) (1 - 7 x)), {x, 0, 30}], x] (* Vincenzo Librandi, Oct 04 2014 *)
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PROG
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(Magma) [7^n -2^n: n in [0..30]];
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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