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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
1, 2, 2, 4, 7, 14, 26, 49, 91, 170, 317, 592, 1105, 2063, 3851, 7189, 13420, 25052, 46766, 87301, 162970, 304226, 567917, 1060165, 1979074, 3694457, 6896666, 12874423, 24033463, 44864717, 83751677, 156344314, 291857374 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
LINKS
FORMULA
a(n)=2*a(n-1)-a(n-3)+a(n-4); 4 initial terms required.
G.f.: (1-2x^2+x^3)/(1-2x+x^3-x^4). - Ralf Stephan, Mar 11 2003
Asymptotic to b*c^n, with b=0.617072414.., c=1.8667604.. - Ralf Stephan, Mar 11 2003
MATHEMATICA
LinearRecurrence[{2, 0, -1, 1}, {1, 2, 2, 4}, 40] (* Harvey P. Dale, Sep 03 2018 *)
CROSSREFS
Sequence in context: A109070 A169973 A300353 * A120363 A118988 A049904
KEYWORD
nonn
AUTHOR
STATUS
approved

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Last modified February 23 14:24 EST 2024. Contains 370283 sequences. (Running on oeis4.)