A272693 - OEIS

%I #11 Jun 07 2016 22:36:02

%S 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 -21,-12,5,14,9,-5,-19,-17,-4,15,16,1,-15,-21,-12,11,20,9,-11,-25,-17,

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

%H N. J. A. Sloane, <a href="/A272693/b272693.txt">Table of n, a(n) for n = 0..10000</a>

%p M:=1000;

%p a:=Array(0..M,0); # A108618 (with different offset)

%p b:=Array(0..M,0); # A108619 (with different offset)

%p c:=Array(0..M,0); # A272693

%p f:=n->sign(n)*(n mod 2);

%p a[0]:=0; b[0]:=0; c[0]:=0;

%p for n from 1 to M do

%p b[n]:=1+(a[n-1]+b[n-1])/2;

%p a[n]:=1+c[n-1]+f(c[n-1])+3*f(b[n]-1);

%p c[n]:=(a[n]-3*b[n])/2;

%p od:

%p [seq(a[n],n=0..M)];

%p [seq(b[n],n=0..M)];

%p [seq(c[n],n=0..M)];

%Y Cf. A108618, A108619.

%K sign

%O 0,3

%A _N. J. A. Sloane_, Jun 07 2016