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 A141124 #5 Jun 13 2015 00:52:38 %S A141124 1,5,-9,-9,17,13,-25,-17,33,21,-41,-25,49,29,-57,-33,65,37,-73,-41,81, %T A141124 45,-89,-49,97,53,-105,-57,113,61,-121,-65,129,69,-137,-73,145,77, %U A141124 -153,-81,161,85,-169,-89,177,93,-185,-97,193,101,-201 %N A141124 Hankel transform of a transform of Jacobsthal numbers. %C A141124 Hankel transform of A100096(n+1). %H A141124 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,-2,0,-1) %F A141124 G.f.: (1+5x-7x^2+x^3)/(1+2x^2+x^4); a(n)=(4n+1)*cos(pi*n/2)+(2n+3)*sin(pi*n/2); %Y A141124 Cf. A017077 (unsigned bisection), A016813 (unsigned bisection). %K A141124 easy,sign %O A141124 0,2 %A A141124 _Paul Barry_, Jun 05 2008