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A065179
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Number of site swap patterns with 3 balls and exact period n.
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4
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1, 3, 12, 42, 156, 554, 2028, 7350, 26936, 98874, 365196, 1353520, 5039580, 18831306, 70626140, 265741350, 1002984060, 3796211692, 14406086604, 54801192684, 208932673508, 798218225802, 3055417434732, 11716355452900
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OFFSET
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1,2
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LINKS
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EXAMPLE
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We have one period 1 (3, the three-ball cascade), three period two (42/24, 51/15 = three-ball shower and 60/06) and twelve period three 3-ball siteswaps (423, 441, 450, 522, 531, 603, 612, 630, 711, 720, 801, 900) (The average of digits is always 3).
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MAPLE
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[seq(DistSS(p, 3), p=1..60)];
add( mobius(n/d)*(4^d-3^d), d=numtheory[divisors](n)) /n ;
end proc:
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MATHEMATICA
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a[n_] := DivisorSum[n, MoebiusMu[n/#]*(4^# - 3^#)&]/n; Array[a, 25] (* Jean-François Alcover, Mar 06 2016 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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