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A120623 Numbers n such that the n-th Catalan number C(2n, n)/(n + 1) is divisible by n/3 but not divisible by n. 3
3, 12, 18, 84, 99, 120, 198, 216, 273, 342, 432, 522, 540, 792, 828, 945, 975, 984, 990, 1035, 1071, 1323, 1377, 1512, 1548, 1575, 1710, 1755, 1863, 2052, 2106, 2226, 2385, 2442, 2790, 2928, 3009, 3015, 3132, 3198, 3483, 3672, 3807, 3915, 3996, 4212, 4428 (list; graph; refs; listen; history; internal format)
OFFSET

1,1

MATHEMATICA

fQ[n_] := fQ[n_] := IntegerQ[ Binomial[2n, n]/(n(n + 1)/3)] && !IntegerQ[ Binomial[2n, n]/n]; Select[ Range@4463, fQ@# &]

CROSSREFS

Cf. A000108, A014847, A120622.

Sequence in context: A061564 A166038 A052637 * A158517 A043877 A134965

Adjacent sequences:  A120620 A120621 A120622 * A120624 A120625 A120626

KEYWORD

nonn

AUTHOR

Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 19 2006

EXTENSIONS

Better description from Joel Lewis (jblewis(AT)fas.harvard.edu), Nov 15 2006

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Last modified February 16 21:51 EST 2012. Contains 205978 sequences.