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A118112
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a(n) = binomial(3n,n) mod (n+1).
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3
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1, 0, 0, 0, 3, 0, 0, 0, 5, 0, 0, 0, 0, 0, 0, 0, 9, 0, 0, 0, 11, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 17, 0, 0, 0, 19, 0, 0, 0, 21, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 33, 0, 0, 0, 35, 0, 0, 0, 37, 0, 0, 0, 0, 0, 0, 0, 41, 0, 0, 0, 43, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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OFFSET
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1,5
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COMMENTS
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These divisibilities are analogous to those of Catalan numbers. For rather long sequences of consecutive integers, a(n)=0. For the first 10000 integers 9678 residues equals zero. See A118113.
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LINKS
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FORMULA
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a(n) = binomial(3n,n) mod (n+1).
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EXAMPLE
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For n=9, binomial(27,7) = 4686825; 4686825 mod 10 = 5.
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MAPLE
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seq(binomial(3*n, n) mod (n+1), n=1..200); # Robert Israel, May 09 2018
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MATHEMATICA
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Table[Mod[Binomial[3*k, k], k+1], {k, 500}]
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PROG
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(PARI) a(n) = binomial(3*n, n) % (n+1); \\ Michel Marcus, May 10 2018
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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