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A199420
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a(n) = (5*7^n+1)/3.
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1
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2, 12, 82, 572, 4002, 28012, 196082, 1372572, 9608002, 67256012, 470792082, 3295544572, 23068812002, 161481684012, 1130371788082, 7912602516572, 55388217616002, 387717523312012, 2714022663184082, 18998158642288572
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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) = 7*a(n-1)-2.
a(n) = 8*a(n-1)-7*a(n-2).
G.f.: 2*(1-2*x)/((1-x)*(1-7*x)).
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MATHEMATICA
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LinearRecurrence[{8, -7}, {2, 12}, 30] (* Harvey P. Dale, Aug 25 2017 *)
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PROG
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(Magma) [(5*7^n+1)/3: 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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