id:A120623 - OEIS Search Results

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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.

+0
4

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; listen)

	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 this_sequence A158517 A043877 A134965` `Adjacent sequences: A120620 A120621 A120622 this_sequence 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 December 7 08:40 EST 2009. Contains 170430 sequences.

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