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A240829 a(1)=-1, a(2)=0, a(3)=1; thereafter a(n) = Sum(a(n-i-s-a(n-i-1)),i=0..k-1) where s=0, k=3. 1

%I

%S -1,0,1,3,2,4,4,7,4,7,7,9,8,9,11,10,10,13,15,13,13,13,18,15,18,18,18,

%T 18,18,23,23,20,19,23,28,27,23,25,27,28,25,26,28,30,31,32,33,33,32,34,

%U 33,38,36,39,34,36,36,39,39,39,39,44,46,46,43,46,46,44,44,49,49,49,46,51,48,51,51,54,54,54,54,54

%N a(1)=-1, a(2)=0, a(3)=1; thereafter a(n) = Sum(a(n-i-s-a(n-i-1)),i=0..k-1) where s=0, k=3.

%D Callaghan, Joseph, John J. Chew III, and Stephen M. Tanny. "On the behavior of a family of meta-Fibonacci sequences." SIAM Journal on Discrete Mathematics 18.4 (2005): 794-824. See Fig. 1.7.

%H N. J. A. Sloane, <a href="/A240829/b240829.txt">Table of n, a(n) for n = 1..20000</a>

%H <a href="/index/Ho#Hofstadter">Index entries for Hofstadter-type sequences</a>

%p #T_s,k(n) from Callaghan et al. Eq. (1.6).

%p s:=0; k:=3;

%p a:=proc(n) option remember; global s,k;

%p if n <= 3 then n-2

%p else

%p add(a(n-i-s-a(n-i-1)),i=0..k-1);

%p fi; end;

%p t1:=[seq(a(n),n=1..100)];

%Y Same recurrence as A240828, A120503 and A046702.

%K sign,hear

%O 1,4

%A _N. J. A. Sloane_, Apr 16 2014

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Last modified January 28 06:00 EST 2021. Contains 340490 sequences. (Running on oeis4.)