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 A276278 #26 Sep 08 2022 08:46:17
%S A276278 3,5,6,7,9,10,11,12,13,14,16,17,18,19,20,21,23,24,25,26,27,28,30,31,
%T A276278 32,33,34,35,37,38,39,40,41,42,44,45,46,47,48,49,51,52,53,54,55,56,58,
%U A276278 59,60,61,62,63,65,66,67,68,69,70,72,73,74,75,76,77,79
%N A276278 Complement of A026474.
%C A276278 Numbers of the form prime(k)^a(n) do not appear in A026477.
%C A276278 Terms are all the positive integers except 1, 2, 4 and numbers of the form 7k+1.
%H A276278 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,0,0,0,1,-1).
%F A276278 For n>=2, a(n) = n + ceiling((n+2)/6) + 2.
%F A276278 For n>=8, a(n) = a(n-6) + 7.
%F A276278 G.f.: (3+2*x+x^2+x^3+2*x^4+x^5-2*x^6-x^7)/(1-x-x^6+x^7). - _Robert Israel_, Sep 09 2016
%p A276278 3, seq(n + ceil((n+2)/6)+2, n=2..100); # _Robert Israel_, Sep 09 2016
%t A276278 Join[{3}, LinearRecurrence[{1, 0, 0, 0, 0, 1, -1}, {5, 6, 7, 9, 10, 11, 12}, 100]] (* _Vincenzo Librandi_, Aug 27 2016 *)
%o A276278 (PARI) a(n)=if(n>1, n+(n+7)\6, 2) \\ _Charles R Greathouse IV_, Aug 27 2016
%o A276278 (PARI) Vec((3+2*x+x^2+x^3+2*x^4+x^5-2*x^6-x^7)/(1-x-x^6+x^7) + O(x^99)) \\ _Altug Alkan_, Sep 09 2016
%o A276278 (Magma) [n+Ceiling((n+2)/6)+2: n in [0..100]]; // _Vincenzo Librandi_, Aug 27 2016
%Y A276278 Cf. A026474, A026477.
%K A276278 nonn,easy
%O A276278 1,1
%A A276278 _Bob Selcoe_, Aug 26 2016