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A005053
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Expand (1-2*x)/(1-5*x).
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15
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1, 3, 15, 75, 375, 1875, 9375, 46875, 234375, 1171875, 5859375, 29296875, 146484375, 732421875, 3662109375, 18310546875, 91552734375, 457763671875, 2288818359375, 11444091796875, 57220458984375
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OFFSET
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0,2
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COMMENTS
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a(n) is the number of generalized compositions of n when there are 3*2^(i-1) different types of i, (i=1,2,...). - Milan Janjic, Sep 24 2010
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LINKS
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FORMULA
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MATHEMATICA
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CoefficientList[Series[(1-2x)/(1-5x), {x, 0, 30}], x] (* or *) Join[{1}, NestList[5#&, 3, 29]] (* Harvey P. Dale, Apr 25 2011 *)
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PROG
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(Magma) [ n eq 0 select 1 else 3*5^(n-1): n in [0..20] ]; // Klaus Brockhaus, Apr 04 2010
(PARI) x='x+O('x^50); Vec((1-2*x)/(1-5*x)) \\ G. C. Greubel, Sep 15 2017
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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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EXTENSIONS
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STATUS
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approved
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