%I #12 Sep 25 2017 11:25:12

%S 0,0,1,0,0,0,2,-1,0,0,3,-2,0,0,4,-3,0,0,5,-4,0,0,6,-5,0,0,7,-6,0,0,8,

%T -7,0,0,9,-8,0,0,10,-9,0,0,11,-10,0,0,12,-11,0,0,13,-12,0,0,14,-13,0,

%U 0,15,-14,0,0,16,-15,0,0,17,-16,0,0,18,-17,0,0,19,-18,0,0,20,-19,0,0,21,-20,0,0,22,-21,0,0,23,-22,0,0,24,-23,0,0,25,-24,0

%N First differences of A130845.

%H Colin Barker, <a href="/A130507/b130507.txt">Table of n, a(n) for n = 0..1000</a>

%H <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (-1,-1,-1,1,1,1,1).

%F a(n) = (1/16)*(cos(n*Pi/2)+sin(n*Pi/2)-1)*((2n-1)*cos(n*Pi/2)-5*cos(n*Pi)+(2n-1)*sin(n*Pi/2))*(-1)^floor((n-1)/2). - _Wesley Ivan Hurt_, Sep 24 2017

%F From _Colin Barker_, Sep 25 2017: (Start)

%F G.f.: x^2*(1 + x + x^2 + x^3 + x^4) / ((1 - x)*(1 + x)^2*(1 + x^2)^2).

%F a(n) = -a(n-1) - a(n-2) - a(n-3) + a(n-4) + a(n-5) + a(n-6) + a(n-7) for n>6.

%F (End)

%o (PARI) concat(vector(2), Vec(x^2*(1 + x + x^2 + x^3 + x^4) / ((1 - x)*(1 + x)^2*(1 + x^2)^2) + O(x^100))) \\ _Colin Barker_, Sep 25 2017

%Y Cf. A130845.

%K sign,easy

%O 0,7

%A _Paul Curtz_, Aug 16 2007

%E One term corrected by _Colin Barker_, Sep 25 2017