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 A017817 a(n) = a(n-3) + a(n-4), with a(0)=1, a(1)=a(2)=0, a(3)=1. 18

%I

%S 1,0,0,1,1,0,1,2,1,1,3,3,2,4,6,5,6,10,11,11,16,21,22,27,37,43,49,64,

%T 80,92,113,144,172,205,257,316,377,462,573,693,839,1035,1266,1532,

%U 1874,2301,2798,3406,4175,5099,6204,7581,9274,11303,13785,16855,20577,25088

%N a(n) = a(n-3) + a(n-4), with a(0)=1, a(1)=a(2)=0, a(3)=1.

%C Number of permutations satisfying -k<=p(i)-i<=r and p(i)-i not in I, i=1..n, with k=1, r=3, I={0,1}. - _Vladimir Baltic_, Mar 07 2012

%C Number of compositions (ordered partitions) of n into parts 3 and 4.

%H Seiichi Manyama, <a href="/A017817/b017817.txt">Table of n, a(n) for n = 0..10000</a>

%H Vladimir Baltic, <a href="https://doi.org/10.2298/AADM1000008B">On the number of certain types of strongly restricted permutations</a>, Applicable Analysis and Discrete Mathematics 4 (2010), 119-135

%H INRIA Algorithms Project, <a href="http://ecs.inria.fr/services/structure?nbr=484">Encyclopedia of Combinatorial Structures 484</a>

%H Milan Janjic, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL19/Janjic/janjic73.html">Binomial Coefficients and Enumeration of Restricted Words</a>, Journal of Integer Sequences, 2016, Vol 19, #16.7.3

%H E. Wilson, <a href="http://www.anaphoria.com/meruone.PDF">The Scales of Mt. Meru</a>

%H <a href="/index/Tu#2wis">Index entries for two-way infinite sequences</a>

%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,1,1).

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

%F a(n)/a(n-1) tends to A060007. - _Gary W. Adamson_, Oct 22 2006

%F a(n) = Sum_{k=0..floor(n/3)} binomial(k,n-3*k). - _Seiichi Manyama_, Mar 06 2019

%t LinearRecurrence[{0,0,1,1}, {1,0,0,1}, 60] (* _G. C. Greubel_, Mar 05 2019 *)

%o (PARI) a(n)=polcoeff(if(n<0,(1+x)/(1+x-x^4),1/(1-x^3-x^4)) +x*O(x^abs(n)), abs(n))

%o (MAGMA) I:=[1,0,0,1]; [n le 4 select I[n] else Self(n-3) +Self(n-4): n in [1..60]]; // _G. C. Greubel_, Mar 05 2019

%o (Sage) (1/(1-x^3-x^4)).series(x, 60).coefficients(x, sparse=False) # _G. C. Greubel_, Mar 05 2019

%o (GAP) a:=[1,0,0,1];; for n in [5..60] do a[n]:=a[n-3]+a[n-4]; od; a; # _G. C. Greubel_, Mar 05 2019

%Y A003269(n) = a(-4-n)(-1)^n.

%K nonn,easy

%O 0,8

%A _N. J. A. Sloane_

%E More terms from Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de), Dec 17 1999

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Last modified June 24 02:56 EDT 2021. Contains 345415 sequences. (Running on oeis4.)