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%I #15 Sep 16 2018 06:39:09
%S 1,-2,3,-5,9,-17,33,-65,129,-257,513,-1025,2049,-4097,8193,-16385,
%T 32769,-65537,131073,-262145,524289,-1048577,2097153,-4194305,8388609,
%U -16777217,33554433,-67108865,134217729,-268435457,536870913
%N Expansion of (1 + x - x^2)/((1 + x)*(1 + 2*x)).
%C Alternating row sums of A105810. Riordan triangle ((1 + x - x^2)/(1 + x)^2, x/(1 + x)).
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (-3,-2).
%F O.g.f.: (1+x-x^2)/((1+x)*(1+2*x)).
%F a(n) = (3/2)*b(n) + (5/2)*b(n-1), n>=1, a(0) = 1, with b(n) = A225883(n+1).
%F a(n) = (-1)^n*(1 + 2^(n-1)), n>=1, a(0) = 1.
%o (PARI) Vec((1 + x - x^2)/((1 + x)*(1 + 2*x)) + O (x^40)) \\ _Michel Marcus_, Oct 11 2014
%Y Cf. A105810, A094373.
%K sign,easy
%O 0,2
%A _Wolfdieter Lang_, Oct 04 2014
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