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A133448
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a(n) = 3*a(n-1) - a(n-3) + 3*a(n-4).
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2
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2, 5, 13, 40, 121, 365, 1094, 3281, 9841, 29524, 88573, 265721, 797162, 2391485, 7174453, 21523360, 64570081, 193710245, 581130734, 1743392201, 5230176601, 15690529804, 47071589413, 141214768241, 423644304722, 1270932914165, 3812798742493, 11438396227480
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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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G.f.: ( -2+x+2*x^2-3*x^3 ) / ( (3*x-1)*(1+x)*(x^2-x+1) ). - Robert Israel, Jun 08 2017
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MAPLE
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f:= gfun:-rectoproc({a(n)=3*a(n-1)-a(n-3)+3*a(n-4), a(0)=2, a(1)=5, a(2)=13, a(3)=40, a(4)=121}, a(n), remember):
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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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