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A199680
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a(n) = (11*9^n+1)/2.
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1
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6, 50, 446, 4010, 36086, 324770, 2922926, 26306330, 236756966, 2130812690, 19177314206, 172595827850, 1553362450646, 13980262055810, 125822358502286, 1132401226520570, 10191611038685126, 91724499348166130, 825520494133495166
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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) = 9*a(n-1)-4.
a(n) = 10*a(n-1)-9*a(n-2).
G.f.: 2*(3-5*x)/((1-x)*(1-9*x)).
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MATHEMATICA
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PROG
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(Magma) [(11*9^n+1)/2: 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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