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 A140683 #17 Mar 01 2024 11:02:37
%S A140683 -4,5,-13,23,-49,95,-193,383,-769,1535,-3073,6143,-12289,24575,-49153,
%T A140683 98303,-196609,393215,-786433,1572863,-3145729,6291455,-12582913,
%U A140683 25165823,-50331649,100663295,-201326593,402653183,-805306369,1610612735,-3221225473
%N A140683 a(n) = 3*(-1)^(n+1)*2^n - 1.
%C A140683 Alternated reading of negative of A140660 and A140529.
%C A140683 The binomial transform yields -4 followed by the negative of A140657.
%C A140683 The inverse binomial transform yields essentially a signed version of A000244. - _R. J. Mathar_, Aug 02 2008
%H A140683 Vincenzo Librandi, <a href="/A140683/b140683.txt">Table of n, a(n) for n = 0..1000</a>
%H A140683 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (-1, 2).
%F A140683 a(2n) = -A140660(n). a(2n+1) = A140529(n).
%F A140683 a(n+1) - a(n) = (-1)^n*A005010(n). a(2n) + a(2n+1) = A096045(n).
%F A140683 a(n) = A140590(n+1) - 2*A140590(n).
%F A140683 O.g.f: (4-x)/((x-1)(2x+1)). - _R. J. Mathar_, Aug 02 2008
%F A140683 a(n) = -a(n-1) + 2*a(n-2); a(0)=-4, a(1)=5. - _Harvey P. Dale_, May 26 2011
%t A140683 Table[3(-1)^(n+1)2^n-1,{n,0,40}] (* or *) LinearRecurrence[{-1,2},{-4,5},40] (* _Harvey P. Dale_, May 26 2011 *)
%o A140683 (Magma) [3*(-1)^(n+1)*2^n-1: n in [0..40]]; // _Vincenzo Librandi_, Aug 08 2011
%K A140683 sign
%O A140683 0,1
%A A140683 _Paul Curtz_, Jul 11 2008
%E A140683 Edited and extended by _R. J. Mathar_, Aug 02 2008