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A086943 Integers k such that R(k+7) = 3.

%I A086943 #34 Aug 05 2025 12:55:16
%S A086943 23,293,2993,29993,299993,2999993,29999993,299999993,2999999993,
%T A086943 29999999993,299999999993,2999999999993,29999999999993,
%U A086943 299999999999993,2999999999999993,29999999999999993,299999999999999993,2999999999999999993,29999999999999999993,299999999999999999993
%N A086943 Integers k such that R(k+7) = 3.
%H A086943 Vincenzo Librandi, <a href="/A086943/b086943.txt">Table of n, a(n) for n = 1..300</a>
%H A086943 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (11,-10).
%F A086943 a(n) = 3*10^n - 7.
%F A086943 R(a(n)) = A086942(n).
%F A086943 From _Elmo R. Oliveira_, Apr 30 2025: (Start)
%F A086943 G.f.: x*(40*x+23)/((x-1)*(10*x-1)).
%F A086943 E.g.f.: 4 - 7*exp(x) + 3*exp(10*x).
%F A086943 a(n) = 11*a(n-1) - 10*a(n-2) for n > 2. (End)
%t A086943 FromDigits/@Table[Join[{2},Table[9,{n}],{3}],{n,0,20}] (* _Harvey P. Dale_, Aug 21 2011 *)
%t A086943 Table[ 10*FromDigits[PadRight[{2},n,9]]+3,{n,20}] (* _Harvey P. Dale_, Aug 05 2025 *)
%o A086943 (Magma) [3*10^n-7: n in [1..25] ]; // _Vincenzo Librandi_, Aug 22 2011
%o A086943 (Maxima) A086943(n):=3*10^n-7$
%o A086943 makelist(A086943(n),n,1,17); /* _Martin Ettl_, Nov 08 2012 */
%Y A086943 Cf. A004086, A086942.
%K A086943 nonn,base,easy
%O A086943 1,1
%A A086943 _Ray Chandler_, Jul 24 2003