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%I #8 Aug 15 2015 16:07:53
%S 4,4,4,4,0,-12,-32,-52,-52,0,136,356,576,576,0,-1508,-3948,-6388,
%T -6388,0,16724,43784,70844,70844,0,-185472,-485572,-785672,-785672,0,
%U 2056916,5385076,8713236,8713236,0,-22811548,-59721408,-96631268,-96631268,0,252983944,662320564
%N a(n) = A171373(n+1) - 2*A171373(n).
%C The least significant digits have a period of length 20. Another period (not the same but of the same length, as this a sequence contains negative numbers) is defined reading the sequence modulo 10.
%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (3,-4,2,-1)
%F a(n)=4*A105371(n-1), n>0.
%F a(n)= 3*a(n-1) -4*a(n-2) +2*a(n-3) -a(n-4). G.f.: 4*(1-2*x+2*x^2)/(1-3*x+4*x^2-2*x^3+x^4).
%Y Cf. A138112, A105371.
%K sign
%O 0,1
%A _Paul Curtz_, Dec 08 2009
%E Edited and extended by _R. J. Mathar_, Mar 02 2010
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