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 A026055 #14 Mar 17 2021 08:17:33
%S A026055 6,14,25,40,59,84,114,150,192,242,299,364,437,520,612,714,826,950,
%T A026055 1085,1232,1391,1564,1750,1950,2164,2394,2639,2900,3177,3472,3784,
%U A026055 4114,4462,4830,5217,5624,6051,6500,6970,7462,7976,8514,9075,9660,10269,10904,11564,12250,12962,13702,14469,15264
%N A026055 a(n) = (d(n)-r(n))/2, where d = A026054 and r is the periodic sequence with fundamental period (1,0,0,0).
%H A026055 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1,1,-3,3,-1).
%F A026055 a(n) = - 0.125 - 0.125*( - 1)^n - 0.25*cos(n*Pi/2) + (n + 2)*(n + 3)*(n + 13)/12 [From _Richard Choulet_, Dec 13 2008]
%F A026055 a(n) = (n + 2)*(n + 3)*(n + 13)/12 - 0.125 - 0.125*( - 1)^n - 0.25*cos(n*Pi/2) [From _Richard Choulet_, Dec 13 2008]
%F A026055 G.f.: x^3*( 6-4*x+x^2+x^3+6*x^5-2*x^6-6*x^4 ) / ( (1+x)*(x^2+1)*(x-1)^4 ). - _R. J. Mathar_, Jun 22 2013
%t A026055 LinearRecurrence[{3,-3,1,1,-3,3,-1},{6,14,25,40,59,84,114},60] (* _Harvey P. Dale_, Mar 27 2013 *)
%K A026055 nonn,easy
%O A026055 3,1
%A A026055 _Clark Kimberling_