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A125857
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Numbers whose base-9 representation is 22222222.......2.
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5
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0, 2, 20, 182, 1640, 14762, 132860, 1195742, 10761680, 96855122, 871696100, 7845264902, 70607384120, 635466457082, 5719198113740, 51472783023662, 463255047212960, 4169295424916642, 37523658824249780, 337712929418248022
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OFFSET
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1,2
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COMMENTS
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If f(1) := 1/x and f(n+1) = (f(n) + 2/f(n))/3, then f(n) = 3^(1-n) * (1/x + a(n)*x + O(x^3)). - Michael Somos, Jul 28 2020
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LINKS
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FORMULA
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a(n) = (9^(n-1) - 1)*2/8.
a(n) = 10*a(n-1) - 9*a(n-2).
G.f.: 2*x^2 / ((x-1)*(9*x-1)). (End)
a(n) = -a(2-n) * 9^(n-1) for all n in Z. - Michael Somos, Jul 02 2017
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EXAMPLE
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G.f. = 2*x^2 + 20*x^3 + 182*x^4 + 1640*x^5 + 14762*x^6 + 132860*x^7 + ... - Michael Somos, Jul 28 2020
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MAPLE
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seq((9^n-1)*2/8, n=0..19);
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MATHEMATICA
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FromDigits[#, 9]&/@Table[PadRight[{2}, n, 2], {n, 0, 20}] (* Harvey P. Dale, Feb 02 2011 *)
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PROG
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(PARI) Vec(2*x^2/((x-1)*(9*x-1)) + O(x^100)) \\ Colin Barker, Sep 30 2014
(PARI) {a(n) = (9^(n-1) - 1)/4}; /* Michael Somos, Jul 02 2017 */
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CROSSREFS
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KEYWORD
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easy,nonn,base
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AUTHOR
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STATUS
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approved
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