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A120625
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Numbers n such that the n-th Catalan number C(2n,n)/(n+1) is divisible by 3n.
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1
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15, 20, 42, 77, 88, 104, 126, 140, 153, 156, 170, 187, 190, 204, 209, 210, 220, 228, 231, 238, 240, 266, 299, 308, 312, 322, 368, 420, 429, 435, 440, 442, 450, 460, 464, 468, 476, 483, 493, 496, 510, 527, 551, 558, 561, 580, 589, 600, 609, 620, 624, 651, 665
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Equivalently, numbers n such that the n-th central binomial coefficient C(2n,n) is divisible by 3n(n+1). - Joel B. Lewis (jblewis(AT)post.harvard.edu), Jan 07 2008
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MATHEMATICA
| fQ[n_] := fQ[n_] := IntegerQ[ Binomial[2n, n]/(3n(n + 1))]; Select[ Range@681, fQ@# &]
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CROSSREFS
| Subset of A104847, Cf. A120623.
Sequence in context: A065148 A093028 A105506 * A038352 A043125 A043905
Adjacent sequences: A120622 A120623 A120624 * A120626 A120627 A120628
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KEYWORD
| nonn
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 19 2006
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EXTENSIONS
| Definition corrected by Joel Brewster Lewis (jblewis(AT)post.harvard.edu), Apr 30 2009
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