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 A049868 a(n)=Sum{a(k): k=0,1,2,...,n-4,n-2,n-1}; a(n-3) is not a summand; 3 initial terms required. 0

%I #9 Sep 03 2018 13:25:01

%S 1,2,2,4,7,14,26,49,91,170,317,592,1105,2063,3851,7189,13420,25052,

%T 46766,87301,162970,304226,567917,1060165,1979074,3694457,6896666,

%U 12874423,24033463,44864717,83751677,156344314,291857374

%N a(n)=Sum{a(k): k=0,1,2,...,n-4,n-2,n-1}; a(n-3) is not a summand; 3 initial terms required.

%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (2,0,-1,1).

%F a(n)=2*a(n-1)-a(n-3)+a(n-4); 4 initial terms required.

%F G.f.: (1-2x^2+x^3)/(1-2x+x^3-x^4). - _Ralf Stephan_, Mar 11 2003

%F Asymptotic to b*c^n, with b=0.617072414.., c=1.8667604.. - _Ralf Stephan_, Mar 11 2003

%t LinearRecurrence[{2,0,-1,1},{1,2,2,4},40] (* _Harvey P. Dale_, Sep 03 2018 *)

%K nonn

%O 0,2

%A _Clark Kimberling_

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Last modified April 21 19:12 EDT 2024. Contains 371881 sequences. (Running on oeis4.)