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 A166577 #28 Dec 12 2023 07:44:29
%S A166577 1,4,-5,10,-20,40,-80,160,-320,640,-1280,2560,-5120,10240,-20480,
%T A166577 40960,-81920,163840,-327680,655360,-1310720,2621440,-5242880,
%U A166577 10485760,-20971520,41943040,-83886080,167772160,-335544320,671088640,-1342177280,2684354560,-5368709120
%N A166577 Inverse binomial transform of A166517.
%C A166577 The definition assumes that the offset of A166517 is changed to 0.
%C A166577 A166517 mod 9 yields a periodic sequence with period 1, 5, 4, 8, 7, 2.
%C A166577 This set of numbers in the period appears also in A153130, A146501, and A166304.
%H A166577 G. C. Greubel, <a href="/A166577/b166577.txt">Table of n, a(n) for n = 0..1000</a>
%H A166577 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (-2).
%F A166577 a(n) = -2*a(n-1), n>2.
%F A166577 a(n) = (-1)^(n+1)*A020714(n-2), n>1.
%F A166577 From _Colin Barker_, Jan 07 2013: (Start)
%F A166577 a(n) = -5*(-1)^n*2^(n-2) for n>1.
%F A166577 G.f.: (3*x^2+6*x+1)/(2*x+1). (End)
%F A166577 E.g.f.: (9/4) + (3/2)*x - (5/4)*exp(-2*x). - _Alejandro J. Becerra Jr._, Feb 15 2021
%t A166577 Join[{1,4},NestList[-2#&,-5,40]] (* _Harvey P. Dale_, Aug 02 2012 *)
%t A166577 Join[{1, 4}, LinearRecurrence[{-2}, {-5}, 48]] (* _G. C. Greubel_, May 17 2016 *)
%Y A166577 Cf. A010716, A010692, A010859.
%K A166577 sign,easy
%O A166577 0,2
%A A166577 _Paul Curtz_, Oct 17 2009
%E A166577 Edited, comments not concerning this sequence removed, and extended by _R. J. Mathar_, Oct 21 2009