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A272693 a(0)=0; thereafter, a(n) = (A108618(n-1)-3*A108619(n))/2.

%I A272693 #11 Jun 07 2016 22:36:02
%S A272693 0,-1,-2,-5,-4,-3,-3,0,5,2,-3,-6,-7,-5,2,9,4,-5,-10,-9,-3,6,11,5,-10,
%T A272693 -21,-12,5,14,9,-5,-19,-17,-4,15,16,1,-15,-21,-12,11,20,9,-11,-25,-17,
%U A272693 2,21,16,-5,-22,-21,-3,18,23,5,-22,-33,-15,18,35,17,-22,-45,-24,17,38,21,-17,-43,-29,8,39
%N A272693 a(0)=0; thereafter, a(n) = (A108618(n-1)-3*A108619(n))/2.
%H A272693 N. J. A. Sloane, <a href="/A272693/b272693.txt">Table of n, a(n) for n = 0..10000</a>
%p A272693 M:=1000;
%p A272693 a:=Array(0..M,0); # A108618 (with different offset)
%p A272693 b:=Array(0..M,0); # A108619 (with different offset)
%p A272693 c:=Array(0..M,0); # A272693
%p A272693 f:=n->sign(n)*(n mod 2);
%p A272693 a[0]:=0; b[0]:=0; c[0]:=0;
%p A272693 for n from 1 to M do
%p A272693 b[n]:=1+(a[n-1]+b[n-1])/2;
%p A272693 a[n]:=1+c[n-1]+f(c[n-1])+3*f(b[n]-1);
%p A272693 c[n]:=(a[n]-3*b[n])/2;
%p A272693 od:
%p A272693 [seq(a[n],n=0..M)];
%p A272693 [seq(b[n],n=0..M)];
%p A272693 [seq(c[n],n=0..M)];
%Y A272693 Cf. A108618, A108619.
%K A272693 sign
%O A272693 0,3
%A A272693 _N. J. A. Sloane_, Jun 07 2016