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A164907
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a(n) = (3*3^n-(-1)^n)/2.
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3
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1, 5, 13, 41, 121, 365, 1093, 3281, 9841, 29525, 88573, 265721, 797161, 2391485, 7174453, 21523361, 64570081, 193710245, 581130733, 1743392201, 5230176601, 15690529805, 47071589413, 141214768241, 423644304721, 1270932914165
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OFFSET
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0,2
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COMMENTS
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Partial sums are (essentially) in A080926.
First differences are (essentially) in A105723.
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LINKS
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FORMULA
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a(n) = 2*a(n-1)+3*a(n-2) for n > 1; a(0) = 1, a(1) = 5.
G.f.: (1+3*x)/((1+x)*(1-3*x)).
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MAPLE
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MATHEMATICA
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LinearRecurrence[{2, 3}, {1, 5}, 50] (* Harvey P. Dale, Oct 31 2018 *)
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PROG
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(Magma) [ (3*3^n-(-1)^n)/2: n in [0..25] ];
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CROSSREFS
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Equals A046717 without initial term 1 and A080925 without initial term 0. Equals A084182 / 2 from second term onward.
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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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