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 A268044 #26 Apr 15 2023 04:20:10
%S A268044 3,9,13,19,23,29,33,39,43,49,53,59,63,69,73,79,83,89,93,99,103,109,
%T A268044 113,119,123,129,133,139,143,149,153,159,163,169,173,179,183,189,193,
%U A268044 199,203,209,213,219,223,229,233,239,243,249,253,259,263,269,273,279,283,289,293,299
%N A268044 The odd numbers congruent to {3, 4} mod 5.
%C A268044 The odd numbers with terminal digit 3 or 9.
%H A268044 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,-1).
%F A268044 G.f.: x*(3 + 6*x + x^2)/((1 + x)*(1 - x)^2).
%F A268044 a(n) = a(n-1) + a(n-2) - a(n-3).
%F A268044 a(n) = 5*n - (3 - (-1)^n)/2.
%F A268044 a(n) = -A131229(-n+1) with A131229(0) = -3.
%F A268044 Sum_{n>=1} (-1)^(n+1)/a(n) = sqrt((5+sqrt(5))/2)*Pi/10 - 3*log(phi)/(2*sqrt(5)), where phi is the golden ratio (A001622). - _Amiram Eldar_, Apr 15 2023
%t A268044 Table[5 n - (3 - (-1)^n)/2, {n, 1000}] (* or *) Select[ Range [1000], OddQ[#] && MemberQ[{3, 4}, Mod[#, 5]] &]
%t A268044 LinearRecurrence[{1,1,-1},{3,9,13},60] (* _Harvey P. Dale_, Feb 12 2023 *)
%o A268044 (Magma) [5*n-(3-(-1)^n)/2: n in [1..60]]; // _Vincenzo Librandi_, Jan 25 2016
%Y A268044 Cf. A001622, A005408, A045435, A047204, A131229.
%Y A268044 Second bisection of A045572.
%K A268044 nonn,easy
%O A268044 1,1
%A A268044 _Mikk Heidemaa_, Jan 25 2016
%E A268044 Edited by _Bruno Berselli_, Jan 25 2016