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A125220
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Numbers k such that binomial(3k, k) - 1 is prime.
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7
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1, 3, 7, 11, 49, 88, 93, 196, 216, 519, 655, 722, 858, 905, 991, 1654, 2277, 3275, 4214, 5047, 5924, 7359, 7953, 11188, 13286, 14626, 14687, 34365, 36014
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OFFSET
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1,2
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LINKS
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MATHEMATICA
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Do[f=Binomial[3n, n]-1; If[PrimeQ[f], Print[n]], {n, 1, 1000}]
Select[Range[4300], PrimeQ[Binomial[3#, #]-1]&] (* Harvey P. Dale, Aug 24 2017 *)
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PROG
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CROSSREFS
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Cf. A125221 (binomial(3k, k) + 1 is prime).
Cf. A066699 (binomial(2k, k) + 1 is prime).
Cf. A066726 (binomial(2k, k) - 1 is prime).
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KEYWORD
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hard,more,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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