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A005053
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Expand (1-2x)/(1-5x).
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9
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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 2^(i+1) different types of i, (i=1,2,...). [From Milan Janjic, Sep 24 2010]
a(n) is the number of generalized compositions of n when there are 3*2^(i-1) different types of i, (i=1,2,...). [From Milan Janjic, Sep 24 2010]
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LINKS
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Table of n, a(n) for n=0..20.
Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 883
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FORMULA
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Binomial transform of A122117 . - Philippe DELEHAM, Oct 19 2006
a(0)=1, a(n)=3*5^(n-1) for n>=1 . - Philippe DELEHAM, Oct 19 2006
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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]] (* From 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] ];
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CROSSREFS
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Sequence in context: A151326 A063000 A002902 * A183411 A136778 A000266
Adjacent sequences: A005050 A005051 A005052 * A005054 A005055 A005056
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KEYWORD
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nonn,easy
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AUTHOR
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N. J. A. Sloane.
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EXTENSIONS
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Wrong formula deleted and MAGMA program added by Klaus Brockhaus, Apr 04 2010
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STATUS
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approved
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