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 A026048 #11 Apr 01 2018 13:11:05
%S A026048 15,21,28,39,52,68,88,111,140,173,211,255,304,361,424,494,572,657,752,
%T A026048 855,967,1089,1220,1363,1516,1680,1856,2043,2244,2457,2683,2923,3176,
%U A026048 3445,3728,4026,4340,4669,5016,5379,5759,6157,6572,7007,7460,7932,8424,8935,9468,10021,10595,11191
%N A026048 (d(n)-r(n))/5, where d = A026046 and r is the periodic sequence with fundamental period (1,0,4,0,0).
%H A026048 <a href="/index/Rec#order_08">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1,0,1,-3,3,-1)
%F A026048 a(n)=(n + 6)*(n^2 + 6*n + 38)/15 - 1/5*( 1 - 2/5*5^(1/2)*cos(2*n*Pi/5) + 2/5*2^(1/2)*(5 - 5^(1/2))^(1/2)*sin(2*n*Pi/5) + 2/5*5^(1/2)*cos(4*n*Pi/5) - 2/5*2^(1/2)*(5 + 5^(1/2))^(1/2)*sin(4*n*Pi/5)) [From _Richard Choulet_, Dec 14 2008]
%F A026048 G.f. x^6*( 15-24*x+10*x^2+3*x^3-2*x^4-14*x^5+25*x^6-11*x^7 ) / ( (x^4+x^3+x^2+x+1)*(x-1)^4 ). - _R. J. Mathar_, Jun 22 2013
%t A026048 LinearRecurrence[{3,-3,1,0,1,-3,3,-1},{15,21,28,39,52,68,88,111},60] (* _Harvey P. Dale_, Apr 01 2018 *)
%Y A026048 A152889 [From _Richard Choulet_, Dec 14 2008]
%K A026048 nonn
%O A026048 6,1
%A A026048 _Clark Kimberling_