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 A224520 #31 Aug 23 2021 14:01:29
%S A224520 0,1,3,7,15,30,60,120,240,481,963,1927,3855,7710,15420,30840,61680,
%T A224520 123361,246723,493447,986895,1973790,3947580,7895160,15790320,
%U A224520 31580641,63161283,126322567,252645135,505290270,1010580540
%N A224520 Numbers a(n) with property a(n) + a(n+4) = 2^(n+4) - 1 = A000225(n+4).
%C A224520 This is the case k=4 of a(n) + a(n+k) = 2^(n+k) - 1 = A000225(n+k). The sequences A000975, A077854 and A153234 correspond to cases k=1,2 and 3, respectively.
%H A224520 G. C. Greubel, <a href="/A224520/b224520.txt">Table of n, a(n) for n = 0..1000</a>
%H A224520 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (3,-2,0,-1,3,-2).
%F A224520 a(n) + a(n+4) = 2^(n+4) - 1.
%F A224520 From _Joerg Arndt_, Apr 09 2013: (Start)
%F A224520 G.f.: x/((1-x)*(1-2*x)*(1+x^4)).
%F A224520 a(n) = +3*a(n-1) -2*a(n-2) -1*a(n-4) +3*a(n-5) -2*a(n-6). (End)
%F A224520 a(n) = floor(2^(n+4)/17). - _Karl V. Keller, Jr._, Jun 30 2021
%t A224520 CoefficientList[Series[x/((1 - x)*(1 - 2*x)*(1 + x^4)), {x, 0, 50}], x] (* _G. C. Greubel_, Oct 11 2017 *)
%t A224520 LinearRecurrence[{3,-2,0,-1,3,-2},{0,1,3,7,15,30},40] (* _Harvey P. Dale_, Aug 23 2021 *)
%o A224520 (PARI) x='x+O('x^50); concat([0], Vec(x/((1-x)*(1-2*x)*(1+x^4)))) \\ _G. C. Greubel_, Oct 11 2017
%o A224520 (Python) print([2**(n+4)//17 for n in range(31)]) # _Karl V. Keller, Jr._, Jun 30 2021
%Y A224520 Cf. A000975, A077854, A153234.
%K A224520 nonn,easy
%O A224520 0,3
%A A224520 _Arie Bos_, Apr 09 2013