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A328985 First differences of A328984.

%I A328985 #16 May 22 2021 20:30:08
%S A328985 2,4,-2,6,-3,9,-7,11,-8,14,-12,16,-13,19,-17,21,-18,24,-22,26,-23,29,
%T A328985 -27,31,-28,34,-32,36,-33,39,-37,41,-38,44,-42,46,-43,49,-47,51,-48,
%U A328985 54,-52,56,-53,59,-57,61,-58,64,-62,66,-63,69,-67,71,-68,74
%N A328985 First differences of A328984.
%C A328985 This is a simplified version of A328196.
%H A328985 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (-1,0,0,1,1).
%F A328985 If n is a multiple of 4 then a(n) = 5*t+1 where t = n/4;
%F A328985 if n is 2 mod 4 then a(n) = 5*t+4 where t = (n-2)/4;
%F A328985 if n is 1 mod 4 then a(n) = -(5*t-2) where t = (n-1)/4;
%F A328985 if n i s 3 mod 4 then a(n) = -(5*t+2) where t = (n-3)/4.
%F A328985 From _Colin Barker_, Nov 07 2019: (Start)
%F A328985 G.f.: x*(2 + 6*x + 2*x^2 + 4*x^3 + x^4) / ((1+x)*(1-x^4)).
%F A328985 a(n) = -a(n-1) + a(n-4) + a(n-5) for n>5.
%F A328985 (End)
%t A328985 Differences[Table[Which[EvenQ[n],Floor[(5 n/2+1)/2],Mod[n,4]==1,10 (n-1)/4+1,True,10 (n-3)/4+7],{n,70}]] (* _Harvey P. Dale_, Apr 06 2021 *)
%Y A328985 Cf. A328190, A328196, A328984.
%K A328985 sign,easy
%O A328985 1,1
%A A328985 _N. J. A. Sloane_, Nov 06 2019