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A285389
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Denominator of Sum_{k=0..n^2-1} (-1)^k*sqrt(Pi)/(Gamma(1/2-k)*Gamma(1+k))/n.
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6
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1, 32, 32768, 268435456, 70368744177664, 295147905179352825856, 19807040628566084398385987584, 10633823966279326983230456482242756608, 365375409332725729550921208179070754913983135744, 50216813883093446110686315385661331328818843555712276103168
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OFFSET
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1,2
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COMMENTS
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All terms are powers of 2.
Lim_{n->inf} A285388(n)/a(n) = 2/sqrt(Pi).
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LINKS
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FORMULA
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a(n) is the denominator of Sum_{k=0..n^2-1} (binomial(2k,k)/4^k)/n.
a(n) = denominator of n*binomial(2*n^2, n^2)/2^(2*n^2 -1). - Ralf Steiner, Apr 22 2017
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MATHEMATICA
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Table[Denominator[Sum[Binomial[2k, k]/4^k, {k, 0, n^2-1}]/n], {n, 1, 10}]
Denominator[Table[2^(1-2 n^2) n Binomial[2 n^2, n^2], {n, 1, 10}]] (* Ralf Steiner, Apr 22 2017 *)
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PROG
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(Python)
from sympy import binomial, Integer
def a(n): return (Integer(2)**(1-2*n**2) * Integer(n) * binomial(2*n**2, n**2)).denominator() # Indranil Ghosh, Apr 27 2017
(Magma) [Denominator( n*(n^2+1)*Catalan(n^2)/2^(2*n^2-1) ): n in [1..21]]; // G. C. Greubel, Dec 11 2021
(Sage)
def A285389(n): return 2^(2*n^2 - 1 - (n^2).popcount() - valuation(n, 2))
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CROSSREFS
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KEYWORD
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nonn,frac
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AUTHOR
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STATUS
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approved
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