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 A087621 #14 Apr 06 2024 13:31:04 %S A087621 -1,2,4,-56,80,-352,64,2176,-4864,31232,-23552,-14336,217088,-2056192, %T A087621 2375680,-7307264,-4390912,102367232,-169607168,877133824,-397410304, %U A087621 -3042967552,9265217536,-68308434944,62495129600,-78483816448,-342993403904 %N A087621 (1,1) entry of powers of the orthogonal design shown below. %C A087621 -1 +1 +1 -1 -1 +1 -1 -1 %C A087621 +1 +1 -1 -1 -1 -1 -1 +1 %C A087621 +1 +1 +1 +1 +1 +1 -1 +1 %C A087621 +1 -1 +1 -1 +1 -1 -1 -1 %C A087621 +1 -1 +1 -1 -1 +1 +1 +1 %C A087621 +1 +1 -1 -1 +1 +1 +1 -1 %C A087621 -1 +1 +1 -1 +1 -1 +1 +1 %C A087621 +1 +1 +1 +1 -1 -1 +1 -1 %D A087621 S. Severini, A note on two integer sequences arising from the 3-dimensional hypercube, Technical Report, Department of Computer Science, University of Bristol, Bristol, UK (October 2003). %H A087621 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,4,0,-64). %F A087621 a(0)=1, a(1)=-1, a(2)=2, a(3)=4, a(n) = 4*a(n-2) - 64*a(n-4). - _T. D. Noe_, Dec 11 2006 %F A087621 G.f.: -x*(4*x+1)*(16*x^2-6*x+1)/(64*x^4-4*x^2+1). - _Colin Barker_, Aug 10 2012 %K A087621 easy,sign %O A087621 1,2 %A A087621 _Simone Severini_, Oct 25 2003 %E A087621 Corrected by _T. D. Noe_, Dec 11 2006