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 A047354 #45 Sep 08 2022 08:44:57
%S A047354 0,1,2,7,8,9,14,15,16,21,22,23,28,29,30,35,36,37,42,43,44,49,50,51,56,
%T A047354 57,58,63,64,65,70,71,72,77,78,79,84,85,86,91,92,93,98,99,100,105,106,
%U A047354 107,112,113,114,119,120,121,126,127,128,133,134,135,140,141
%N A047354 Numbers that are congruent to {0, 1, 2} mod 7.
%H A047354 Vincenzo Librandi, <a href="/A047354/b047354.txt">Table of n, a(n) for n = 1..3000</a>
%H A047354 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (1, 0, 1, -1).
%F A047354 a(n) = 7*floor(n/3)+(n mod 3), with offset 0 and a(0)=0. - _Gary Detlefs_, Mar 09 2010
%F A047354 From _R. J. Mathar_, Mar 29 2010: (Start)
%F A047354 G.f.: x^2*(1+x+5*x^2)/((1+x+x^2) * (x-1)^2).
%F A047354 a(n) = a(n-1) + a(n-3) - a(n-4) for n>4. (End)
%F A047354 a(n+1) = Sum_{k>=0} A030341(n,k)*b(k) with b(0)=1 and b(k)=7*3^(k-1) for k>0. - _Philippe Deléham_, Oct 24 2011
%F A047354 From _Wesley Ivan Hurt_, Jun 08 2016: (Start)
%F A047354 a(n) = (21*n-33-12*cos(2*n*Pi/3)+4*sqrt(3)*sin(2*n*Pi/3))/9.
%F A047354 a(3k) = 7k-5, a(3k-1) = 7k-6, a(3k-2) = 7k-7. (End)
%F A047354 a(n) = n + 4*floor((n-1)/3) - 1. - _Bruno Berselli_, Feb 06 2017
%p A047354 seq(7*floor(n/3)+(n mod 3), n=0..60); # _Gary Detlefs_, Mar 09 2010
%t A047354 Flatten[{#,#+1,#+2}&/@(7Range[0,20])] (* _Harvey P. Dale_, Mar 05 2011 *)
%o A047354 (Magma) [n : n in [0..150] | n mod 7 in [0..2]]; // _Wesley Ivan Hurt_, Jun 08 2016
%Y A047354 Cf. A030341.
%Y A047354 Cf. similar sequences with formula n+i*floor(n/3) listed in A281899.
%K A047354 nonn,easy
%O A047354 1,3
%A A047354 _N. J. A. Sloane_