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 A134967 #28 Nov 20 2024 15:55:47
%S A134967 -1,2,-1,2,-3,4,-3,4,-5,6,-5,6,-7,8,-7,8,-9,10,-9,10,-11,12,-11,12,
%T A134967 -13,14,-13,14,-15,16,-15,16,-17,18,-17,18,-19,20,-19,20,-21,22,-21,
%U A134967 22,-23,24,-23,24,-25,26,-25,26,-27,28,-27,28,-29,30,-29,30,-31,32,-31,32,-33,34,-33,34,-35,36,-35,36,-37,38,-37,38,-39
%N A134967 List of quadruples: [-2n-1, 2n+2, -2n-1, 2n+2].
%C A134967 First differences are 3, -3, 3, -5, 7, -7, 7, -9, 11, -11, 11, ... .
%H A134967 Colin Barker, <a href="/A134967/b134967.txt">Table of n, a(n) for n = 0..1000</a>
%H A134967 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (-1,0,0,1,1).
%F A134967 a(n) = (1-(2*n+3)*(-1)^n-2*(-1)^((2*n+1-(-1)^n)/4))/4. - _Luce ETIENNE_, Sep 04 2016
%F A134967 a(n) = cos((n-1)*Pi)*(2*n+3+2*cos(n*Pi/2)-cos(n*Pi)+2*sin(n*Pi/2))/4. - _Wesley Ivan Hurt_, Oct 02 2017
%F A134967 From _Colin Barker_, Oct 05 2017: (Start)
%F A134967 G.f.: -(1 - x - x^2 - x^3) / ((1 - x)*(1 + x)^2*(1 + x^2)).
%F A134967 a(n) = (1 - 3*(-1)^n - (1-i)*(-i)^n - (1+i)*i^n - 2*(-1)^n*n) / 4 were i=sqrt(-1).
%F A134967 (End)
%t A134967 Flatten[Table[{-2n-1,2n+2,-2n-1,2n+2},{n,0,20}]] (* _Harvey P. Dale_, Oct 19 2011 *)
%o A134967 (Magma) [(1-(2*n+3)*(-1)^n-2*(-1)^((2*n+1-(-1)^n)div 4))/4: n in [0..80]]; // _Vincenzo Librandi_, Oct 04 2017
%o A134967 (Magma) &cat [[-2*n-1,2*n+2,-2*n-1,2*n+2]: n in [0..30]]; // _Vincenzo Librandi_, Oct 04 2017
%o A134967 (PARI) Vec(-(1 - x - x^2 - x^3) / ((1 - x)*(1 + x)^2*(1 + x^2)) + O(x^100)) \\ _Colin Barker_, Oct 05 2017
%K A134967 sign,easy
%O A134967 0,2
%A A134967 _Paul Curtz_, Feb 04 2008