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 A154119 Numbers n such that binomial(3n,n) is odd and not divisible by 5. 1
 0, 1, 5, 8, 16, 33, 40, 41, 65, 66, 80, 81, 128, 130, 133, 138, 165, 325, 328, 330, 640, 641, 650, 656, 658, 1025, 1026, 1028, 1033, 1040, 1041, 2065, 2066, 2080, 2081, 4128, 4130, 4133, 4138, 4165, 4688, 4690, 4753, 4756, 4776, 4778, 5125, 5128, 5130, 5138 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS From the first 10001 terms of A005809 only 80 are odd and not divisible by 5. LINKS Chai Wah Wu, Table of n, a(n) for n = 0..4000 FORMULA A005809(a(n)) is odd and not divisible by 5. MATHEMATICA (*M6*)Reap[Do[b=Binomial[3n, n]; If[OddQ[b]&&Mod[b, 10]=/=5, Sow[n]], {n, 100}]][[2, 1]] bQ[n_]:=Module[{bi=Binomial[3n, n]}, OddQ[bi]&&!Divisible[bi, 5]]; Select[Range[0, 5300], bQ] (* Harvey P. Dale, Jul 19 2011 *) CROSSREFS Cf. A125221 Numbers n such that binomial(3n,n)+1 is prime, A005809 Binomial coefficients C(3n,n). Sequence in context: A340997 A058566 A153363 * A196387 A258787 A185103 Adjacent sequences: A154116 A154117 A154118 * A154120 A154121 A154122 KEYWORD nonn AUTHOR Zak Seidov, Jan 05 2009 EXTENSIONS Corrected definition - Harvey P. Dale, Jul 19 2011 STATUS approved

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Last modified February 24 05:36 EST 2024. Contains 370291 sequences. (Running on oeis4.)