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A120624
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Numbers n such that the n-th Catalan number C(2n,n)/(n+1) is divisible by 2n.
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3
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6, 28, 42, 45, 66, 77, 91, 110, 126, 140, 153, 156, 170, 187, 190, 204, 209, 210, 220, 228, 231, 238, 266, 276, 299, 308, 312, 315, 322, 325, 330, 345, 378, 414, 420, 429, 435, 440, 442, 450, 459, 460, 468, 476, 483, 493, 496, 510, 527, 551, 558, 561, 570
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OFFSET
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1,1
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COMMENTS
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Equivalently, numbers such that the n-th central binomial coefficient C(2n, n) is divisible by 2n(n + 1). - Joel B. Lewis, Jan 07 2008
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LINKS
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MATHEMATICA
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fQ[n_] := fQ[n_] := IntegerQ[ Binomial[2n, n]/(2n(n + 1))]; Select[ Range@8719, fQ@# &]
Select[Range[600], Divisible[CatalanNumber[#], 2#]&] (* Harvey P. Dale, Aug 30 2016 *)
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PROG
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(Python)
from __future__ import division
for n in range(1, 10**5):
if not b % (2*n):
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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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