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A199561
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a(n) = 3*9^n+1.
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4
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4, 28, 244, 2188, 19684, 177148, 1594324, 14348908, 129140164, 1162261468, 10460353204, 94143178828, 847288609444, 7625597484988, 68630377364884, 617673396283948, 5559060566555524, 50031545098999708, 450283905890997364
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OFFSET
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0,1
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COMMENTS
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An Engel expansion of 3 to the base 9 as defined in A181565, with the associated series expansion 3 = 9/4 + 9^2/(4*28) + 9^3/(4*28*244) + 9^4/(4*28*244*2188) + .... Cf. A087289 and A207262. - Peter Bala, Oct 29 2013
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LINKS
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FORMULA
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a(n) = 9*a(n-1)-8.
a(n) = 10*a(n-1)-9*a(n-2).
G.f.: 4*(1-3*x)/((1-x)*(1-9*x)).
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MATHEMATICA
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3*9^Range[0, 20]+1 (* or *) LinearRecurrence[{10, -9}, {4, 28}, 20] (* Harvey P. Dale, Jul 30 2019 *)
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PROG
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(Magma) [3*9^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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