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A169609
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Period 3: repeat [1, 3, 3].
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10
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1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3
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OFFSET
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0,2
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COMMENTS
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Also continued fraction expansion of (5+sqrt(65))/10 = 1.3062257748....
Also decimal expansion of 133/999.
Inverse binomial transform of A168673.
Essentially first differences of A047347.
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LINKS
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FORMULA
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a(n) = a(n-3) for n > 2, with a(0) = 1, a(1) = 3, a(2) = 3.
G.f.: (1+3*x+3*x^2)/(1-x^3).
a(n) = (7/3)+(2/3)*cos((2*Pi/3)*(n+1))-(2*sqrt(3)/3)*sin((2*Pi/3)*(n+1)). [Richard Choulet, Mar 15 2010]
a(n) = a(n-a(n-2)) for n>=2. Example: a(5) = a(5-a(3)) = a(5-a(3-a(1))) = a(5-a(3-3)) = a(5-a(0)) = a(5-1) = a(4) = a(4-a(2)) = a(4-3) = a(1) = 3. [Richard Choulet, Mar 15 2010; edited by Klaus Brockhaus, Nov 21 2010]
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MAPLE
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MATHEMATICA
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PadRight[{}, 120, {1, 3, 3}] (* or *) LinearRecurrence[{0, 0, 1}, {1, 3, 3}, 120] (* Harvey P. Dale, Apr 29 2015 *)
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PROG
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(Magma) [ n mod 3 eq 0 select 1 else 3: n in [0..104] ];
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CROSSREFS
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Cf. A000012 (all 1's sequence), A010701 (all 3's sequence), A144437 (repeat 3, 3, 1), A154595 (repeat 1, 3, 3, -1, -3, -3), A168615, A168673, A047347 (congruent to {0, 1, 4} mod 7), A010684 (repeat 1, 3).
Cf. A171419 (decimal expansion of (5+sqrt(65))/10).
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KEYWORD
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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