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 A086949 #25 May 02 2025 12:52:54 %S A086949 41,491,4991,49991,499991,4999991,49999991,499999991,4999999991, %T A086949 49999999991,499999999991,4999999999991,49999999999991, %U A086949 499999999999991,4999999999999991,49999999999999991,499999999999999991,4999999999999999991,49999999999999999991,499999999999999999991 %N A086949 Numbers k such that R(k+9) = 5. %H A086949 Vincenzo Librandi, <a href="/A086949/b086949.txt">Table of n, a(n) for n = 1..300</a> %H A086949 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (11,-10). %F A086949 a(n) = 5*10^n - 9. %F A086949 R(a(n)) = A086946(n). %F A086949 From _Stefano Spezia_, Dec 15 2022: (Start) %F A086949 O.g.f.: x*(41 + 40*x)/((1 - x)*(1 - 10*x)). %F A086949 E.g.f.: 4 - 9*exp(x) + 5*exp(10*x). %F A086949 a(n) = 11*a(n-1) - 10*a(n-2) for n > 2. (End) %t A086949 5*10^Range[20]-9 (* _Harvey P. Dale_, Nov 29 2018 *) %o A086949 (Magma) [5*10^n-9: n in [1..25] ]; // _Vincenzo Librandi_, Aug 22 2011 %Y A086949 Cf. A004086, A086946. %K A086949 nonn,base,easy %O A086949 1,1 %A A086949 _Ray Chandler_, Jul 24 2003