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%I #3 Mar 30 2012 18:51:58
%S 2,-1,4,0,12,4,44,20,172,84,684,340,2732,1364,10924,5460,43692,21844,
%T 174764,87380,699052,349524,2796204,1398100,11184812,5592404,44739244,
%U 22369620,178956972,89478484,715827884,357913940,2863311532,1431655764,11453246124
%N Second differences of Jacobsthal sequence A001045, pairs with even and odd indices swapped.
%C The second differences are -1, 2, 0, 4, 4, 12, 20, 44, ... (-1)^(n+1)*A084247(n), essentially A097073, which are listed here with -1 <=> 2, 0 <=> 4 etc. swapped in pairs.
%F a(n) = 4*A092808(n-2), n>1.
%F a(n+1) - 2a(n) = (-1)^n*A140504(n).
%F O.g.f.: (2+x-5x^2)/[(1+x)(1-2x)(1+2x)]. - _R. J. Mathar_, Jul 08 2008
%K sign,less
%O 0,1
%A _Paul Curtz_, Jun 30 2008
%E Edited by _R. J. Mathar_, Jul 08 2008
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