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6, 69, 699, 6999, 69999, 699999, 6999999, 69999999, 699999999, 6999999999, 69999999999, 699999999999, 6999999999999, 69999999999999, 699999999999999, 6999999999999999, 69999999999999999, 699999999999999999
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,1
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LINKS
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FORMULA
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a(n) = 10*a(n-1)+9. a(n) = 11*a(n-1)-10*a(n-2), n>1.
G.f. ( 6+3*x ) / ( (10*x-1)*(x-1) ). - R. J. Mathar, Oct 29 2011
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MATHEMATICA
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NestList[10#+9&, 6, 20] (* or *) LinearRecurrence[{11, -10}, {6, 69}, 20] (* Harvey P. Dale, Dec 29 2013 *)
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PROG
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(Magma) [7*10^n-1: 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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