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 A026047 #8 Jun 13 2015 00:49:05 %S A026047 38,52,72,97,130,170,220,279,350,432,528,637,762,902,1060,1235,1430, %T A026047 1644,1880,2137,2418,2722,3052,3407,3790,4200,4640,5109,5610,6142, %U A026047 6708,7307,7942,8612,9320,10065,10850,11674,12540,13447,14398,15392,16432,17517,18650,19830,21060,22339,23670 %N A026047 a(n) = (d(n)-r(n))/2, where d = A026046 and r is the periodic sequence with fundamental period (0,1,0,1). %H A026047 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (3,-2,-2,3,-1). %F A026047 a(n)=(n + 6)*(n^2 + 6*n + 38)/6 - 0.5*sin(n*Pi/2)^2 [From _Richard Choulet_, Dec 13 2008] %F A026047 G.f. x^6*( 38-62*x-8*x^2+61*x^3-27*x^4 ) / ( (1+x)*(x-1)^4 ). - _R. J. Mathar_, Jun 22 2013 %K A026047 nonn %O A026047 6,1 %A A026047 _Clark Kimberling_