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A020699
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Expansion of (1-3*x)/(1-5*x).
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5
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1, 2, 10, 50, 250, 1250, 6250, 31250, 156250, 781250, 3906250, 19531250, 97656250, 488281250, 2441406250, 12207031250, 61035156250, 305175781250, 1525878906250, 7629394531250, 38146972656250, 190734863281250, 953674316406250
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Partial sums are A034478.
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LINKS
| Nathaniel Johnston, Table of n, a(n) for n = 0..250
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 1037 (archived version of page)
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FORMULA
| a(n) = 2*5^(n-1) for n>0.
E.g.f.: (2*exp(5*x)+3)/5; a(n)=(2*5^n+3*0^n)/5. - Paul Barry (pbarry(AT)wit.ie), Sep 03 2003
a(n)=sum{k=0..n, C(n-1, k)*(Jac(2n-2k)+Jac(2n-2k-1))}+0^n/2, where Jac(n)=A001045(n). - Paul Barry (pbarry(AT)wit.ie), Jun 07 2005
a(0)=1, a(1)=2, a(n)=5*a(n-1) for n>=2. [From Vincenzo Librandi, Jan 01 2011]
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MAPLE
| seq(`if`(n=0, 1, 2*5^(n-1)), n=0..22); # Nathaniel Johnston, Jun 26 2011
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CROSSREFS
| Cf. A034478.
Sequence in context: A015945 A015954 A015949 * A020729 A110170 A026332
Adjacent sequences: A020696 A020697 A020698 * A020700 A020701 A020702
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KEYWORD
| nonn,easy
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AUTHOR
| David W. Wilson (davidwwilson(AT)comcast.net)
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