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A233820 Period 4: repeat [20, 5, 15, 10]. 0
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Clockwise sectors around outside of London Fives dartboard.

LINKS

Table of n, a(n) for n=1..70.

Wikipedia, Darts

Index entries for linear recurrences with constant coefficients, signature (0,0,0,1).

FORMULA

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)

MAPLE

seq(op([20, 5, 15, 10]), n=0..50); # Wesley Ivan Hurt, Jul 07 2016

MATHEMATICA

Flatten[Table[{20, 5, 15, 10}, {17}]]

PROG

(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

CROSSREFS

Cf. A003833.

Sequence in context: A309321 A104158 A068612 * A040387 A201137 A040385

Adjacent sequences:  A233817 A233818 A233819 * A233821 A233822 A233823

KEYWORD

nonn,easy

AUTHOR

Arkadiusz Wesolowski, Dec 16 2013

STATUS

approved

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Last modified April 12 18:58 EDT 2021. Contains 342932 sequences. (Running on oeis4.)