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 A174737 #25 Sep 01 2025 20:28:11 %S A174737 2,-1,-3,-2,1,3,2,-1,-3,-2,1,3,2,-1,-3,-2,1,3,2,-1,-3,-2,1,3,2,-1,-3, %T A174737 -2,1,3,2,-1,-3,-2,1,3,2,-1,-3,-2,1,3,2,-1,-3,-2,1,3,2,-1,-3,-2,1,3,2, %U A174737 -1,-3,-2,1,3,2,-1,-3,-2,1,3,2,-1,-3,-2,1,3,2,-1,-3,-2 %N A174737 a(n) = a(n-1) - a(n-2), with a(0)=2, a(1)=-1. %D A174737 Rosen, Discrete Mathematics and its Applications, McGraw-Hill, 2007, p. 456, Question 1b. %H A174737 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (1,-1). %F A174737 G.f.: ( 2-3*x ) / ( 1-x+x^2 ). - _R. J. Mathar_, Jan 08 2011 %F A174737 a(n) = 2*cos(n*Pi/3)-4*sin(n*Pi/3)/sqrt(3). - _Wesley Ivan Hurt_, Sep 01 2025 %p A174737 a[0] := 2: a[1] := -1: for n from 2 to 80 do a[n] := a[n-1]-a[n-2] end do: seq(a[n], n = 0 .. 75); # _Emeric Deutsch_, Apr 05 2010 %K A174737 sign,easy,changed %O A174737 0,1 %A A174737 Zachary Berger (zsb1244(AT)rit.edu), Mar 28 2010 %E A174737 Typo in definition fixed by _Emeric Deutsch_, Apr 05 2010