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A261130
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a(n) = Product(p prime | n < p <= 2*n).
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4
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1, 2, 3, 5, 35, 7, 77, 143, 143, 2431, 46189, 4199, 96577, 7429, 7429, 215441, 6678671, 392863, 392863, 765049, 765049, 31367009, 1348781387, 58642669, 2756205443, 2756205443, 2756205443, 146078888479, 146078888479, 5037203051, 297194980009, 584803025179
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OFFSET
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0,2
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COMMENTS
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a(n) is a divisor of binomial(2*n, n); the quotient binomial(2*n, n) / a(n) is A263931(n). - Robert FERREOL, Sep 03 2022
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LINKS
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EXAMPLE
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a(0) = 1 because the empty product is 1 by convention.
a(4) = 35 because {p prime | 4 < p <= 8} = {5, 7}.
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MAPLE
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a := n -> convert(select(isprime, {$n+1..2*n}), `*`):
print(seq(a(n), n=0..31));
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MATHEMATICA
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Join[{1}, Table[Times@@Prime[Range[PrimePi[n]+1, PrimePi[2n]]], {n, 40}]] (* Harvey P. Dale, May 09 2017 *)
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PROG
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(Python)
from sympy import primorial
def A261130(n): return primorial(n<<1, nth=False)//primorial(n, nth=False) if n else 1 # Chai Wah Wu, Sep 07 2022
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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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