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A233820
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Period 4: repeat [20, 5, 15, 10].
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0
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20, 5, 15, 10, 20, 5, 15, 10, 20, 5, 15, 10, 20, 5, 15, 10, 20, 5, 15, 10, 20, 5, 15, 10, 20, 5, 15, 10, 20, 5, 15, 10, 20, 5, 15, 10, 20, 5, 15, 10, 20, 5, 15, 10, 20, 5, 15, 10, 20, 5, 15, 10, 20, 5, 15, 10, 20, 5, 15, 10, 20, 5, 15, 10, 20, 5, 15, 10, 20, 5
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refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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Clockwise sectors around outside of London Fives dartboard.
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LINKS
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Table of n, a(n) for n=1..70.
Wikipedia, Darts
Index entries for linear recurrences with constant coefficients, signature (0,0,0,1).
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FORMULA
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From Bruno Berselli, Dec 16 2013: (Start)
G.f.: 5*x*(4 + x + 3*x^2 + 2*x^3)/((1 - x)*(1 + x)*(1 + x^2)).
a(n) = 5*(I^(n*(n-1)) - 2*(-1)^n + 5)/2. (End)
From Wesley Ivan Hurt, Jul 07 2016: (Start)
a(n) = 5*(5 + cos(n*Pi/2) - 2*cos(n*Pi) + sin(n*Pi/2) - 2*I*sin(n*Pi))/2.
a(n) = a(n-4) for n>4. (End)
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MAPLE
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seq(op([20, 5, 15, 10]), n=0..50); # Wesley Ivan Hurt, Jul 07 2016
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MATHEMATICA
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Flatten[Table[{20, 5, 15, 10}, {17}]]
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PROG
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(MAGMA) &cat[[20, 5, 15, 10]: n in [1..17]]; // Bruno Berselli, Dec 16 2013
(PARI) a(n)=[10, 20, 5, 15][n%4+1] \\ Charles R Greathouse IV, Aug 20 2015
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CROSSREFS
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Cf. A003833.
Sequence in context: A309321 A104158 A068612 * A040387 A201137 A040385
Adjacent sequences: A233817 A233818 A233819 * A233821 A233822 A233823
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KEYWORD
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nonn,easy
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AUTHOR
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Arkadiusz Wesolowski, Dec 16 2013
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STATUS
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approved
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