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%I #8 Jun 13 2015 00:50:02
%S 1,2,4,6,11,20,38,71,133,248,463,864,1613,3011,5621,10493,19588,36566,
%T 68260,127425,237872,444050,828935,1547423,2888668,5392451,10066414,
%U 18791583,35079383,65484803,122244437,228201074,425996728
%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.
%t LinearRecurrence[{2,0,-1,1},{1,2,4,6},40] (* _Harvey P. Dale_, Mar 23 2015 *)
%K nonn
%O 0,2
%A _Clark Kimberling_
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