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A260636
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a(n) = binomial(3n, n) mod n.
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3
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0, 1, 0, 3, 3, 0, 3, 7, 3, 5, 3, 0, 3, 8, 9, 15, 3, 15, 3, 15, 0, 4, 3, 12, 3, 2, 3, 12, 3, 24, 3, 15, 18, 15, 0, 9, 3, 34, 6, 31, 3, 21, 3, 0, 15, 38, 3, 36, 3, 40, 33, 40, 3, 42, 0, 16, 27, 44, 3, 0, 3, 46, 45, 47, 39, 51, 3, 53, 15, 0, 3, 45, 3, 15, 9, 20, 76, 0, 3, 7, 3
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listen;
history;
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OFFSET
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1,4
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COMMENTS
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See A059288 for the "2n" analog. Sequence A260640 yields the indices of zeros (analog to A014847 for 2n).
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LINKS
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EXAMPLE
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n=1: C(3,1) = 3 = 0 (mod 1).
n=2: C(3*2,2) = 15 = 1 (mod 2).
n=3: C(3*3,3) = 84 = 0 (mod 3).
n=4: C(3*4,4) = 495 = 3 (mod 4).
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MAPLE
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MATHEMATICA
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PROG
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(PARI) a(n)=binomial(3*n, n)%n
(PARI) A260636(n)=lift(binomod(3*n, n, n)) \\ using binomod.gp by M. Alekseyev, cf. Links.
(Magma) [Binomial(3*n, n) mod n : n in [1..100]]; // Wesley Ivan Hurt, Nov 12 2015
(Python)
from __future__ import division
for n in range(1, 10001):
b = b*3*(3*n+2)*(3*n+1)//((2*n+2)*(2*n+1)) # Chai Wah Wu, Jan 27 2016
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CROSSREFS
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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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