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 A187340 #14 May 10 2024 16:52:09
%S A187340 1,2,5,5,-2,-11,-11,2,17,17,-2,-23,-23,2,29,29,-2,-35,-35,2,41,41,-2,
%T A187340 -47,-47,2,53,53,-2,-59,-59,2,65,65,-2,-71,-71,2,77,77,-2,-83,-83,2,
%U A187340 89,89,-2,-95,-95,2,101,101,-2,-107,-107,2,113,113,-2,-119,-119
%N A187340 Hankel transform of A014301(n+1).
%H A187340 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (2,-3,2,-1).
%F A187340 G.f.: (1+4x^2-x^3)/((1-x+x^2))^2;
%F A187340 a(n) = (1-2n)*cos(Pi*n/3)+(2n+3)*sin(Pi*n/3)/sqrt(3).
%t A187340 LinearRecurrence[{2,-3,2,-1},{1,2,5,5},70] (* _Harvey P. Dale_, Nov 24 2017 *)
%Y A187340 Cf. A014301.
%K A187340 sign,easy
%O A187340 0,2
%A A187340 _Paul Barry_, Mar 08 2011