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 A016190 Expansion of 1/((1-9x)(1-11x)). 4
 1, 20, 301, 4040, 51001, 620060, 7352101, 85656080, 985263601, 11225320100, 126965305501, 1427999420120, 15990423157801, 178436520564140, 1985678518660501, 22048354837360160, 244384923399813601 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS a(n-1), n >= 0, with a(-1) = 0, is also the number of words of length n, over an alphabet of eleven letters, of which any chosen one appears an odd number of times. See the Jul 22 2003 comment in A006516 (4-letter case) and the Balakrishnan reference there. - Wolfdieter Lang, Jul 18 2017 LINKS Index entries for linear recurrences with constant coefficients, signature (20,-99). FORMULA a(n) = (11^(n+1)-9^(n+1))/2. - Bruno Berselli, Feb 09 2011 From Vincenzo Librandi, Feb 09 2011: (Start) a(n) = 11*a(n-1)+9^n, a(0)=1. a(n) = 20*a(n-1)-99*a(n-2), a(0)=1, a(1)=20. (End) MATHEMATICA CoefficientList[Series[1/((1-9x)(1-11x)), {x, 0, 20}], x] (* or *) LinearRecurrence[{20, -99}, {1, 20}, 20] (* Harvey P. Dale, Jun 27 2017 *) PROG (PARI) Vec(1/((1-9*x)*(1-11*x))+O(x^99)) \\ Charles R Greathouse IV, Sep 26 2012 CROSSREFS Cf. A006516, A081203. Sequence in context: A053541 A004345 A001755 * A016188 A006300 A282372 Adjacent sequences:  A016187 A016188 A016189 * A016191 A016192 A016193 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified December 7 00:39 EST 2019. Contains 329815 sequences. (Running on oeis4.)