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A049855
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a(n) = Sum{a(k): k=0,1,2,...,n-3,n-1}; a(n-2) is not a summand; 2 initial terms required.
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0
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2, 3, 3, 5, 10, 18, 31, 54, 95, 167, 293, 514, 902, 1583, 2778, 4875, 8555, 15013, 26346, 46234, 81135, 142382, 249863, 438479, 769477, 1350338, 2369678, 4158495, 7297650, 12806483, 22473811, 39438789, 69210250, 121455522, 213139583, 374033894, 656383727, 1151873143
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OFFSET
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0,1
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LINKS
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FORMULA
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a(n) = 2*a(n-1) - a(n-2) + a(n-3); 3 initial terms required.
G.f.: (2 - x - x^2)/(1 - 2*x + x^2 - x^3). - Stefano Spezia, Sep 10 2022
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MATHEMATICA
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LinearRecurrence[{2, -1, 1}, {2, 3, 3}, 38] (* Stefano Spezia, Sep 10 2022 *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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