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A049859 a(n) = Sum_{k=0,1,2,...,n-4,n-2,n-1} a(k); a(n-3) is not a summand; 3 initial terms required. 0

%I

%S 0,1,3,4,7,12,23,43,81,151,282,526,982,1833,3422,6388,11925,22261,

%T 41556,77575,144814,270333,504647,942055,1758591,3282868,6128328,

%U 11440120,21355963,39866466,74421140,138926437,259342371,484130068

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

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

%F G.f.: x*(x - 1)*(2*x + 1)/(x^4 - x^3 + 2*x - 1). - _Chai Wah Wu_, Jul 29 2020

%K nonn

%O 0,3

%A _Clark Kimberling_

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Last modified January 20 03:25 EST 2022. Contains 350467 sequences. (Running on oeis4.)