This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A016190 #25 Jul 19 2017 07:38:18
%S A016190 1,20,301,4040,51001,620060,7352101,85656080,985263601,11225320100,
%T A016190 126965305501,1427999420120,15990423157801,178436520564140,
%U A016190 1985678518660501,22048354837360160,244384923399813601
%N A016190 Expansion of 1/((1-9x)(1-11x)).
%C A016190 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
%H A016190 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (20,-99).
%F A016190 a(n) = (11^(n+1)-9^(n+1))/2. - _Bruno Berselli_, Feb 09 2011
%F A016190 From _Vincenzo Librandi_, Feb 09 2011: (Start)
%F A016190 a(n) = 11*a(n-1)+9^n, a(0)=1.
%F A016190 a(n) = 20*a(n-1)-99*a(n-2), a(0)=1, a(1)=20. (End)
%t A016190 CoefficientList[Series[1/((1-9x)(1-11x)),{x,0,20}],x] (* or *) LinearRecurrence[{20,-99},{1,20},20] (* _Harvey P. Dale_, Jun 27 2017 *)
%o A016190 (PARI) Vec(1/((1-9*x)*(1-11*x))+O(x^99)) \\ _Charles R Greathouse IV_, Sep 26 2012
%Y A016190 Cf. A006516, A081203.
%K A016190 nonn,easy
%O A016190 0,2
%A A016190 _N. J. A. Sloane_