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 A125244 Numbers k such that binomial(6k, k) - 1 is prime. 5
 1, 7, 17, 22, 43, 343, 381, 461, 543, 923, 1045, 1182, 1486, 1839, 5643, 8260, 9009, 10947, 11793, 15915, 25151 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(22) > 50000. - Robert Price, May 13 2019 LINKS MATHEMATICA Do[f=Binomial[6n, n]-1; If[PrimeQ[f], Print[n]], {n, 1, 1000}] CROSSREFS Cf. A125245 = numbers n such that binomial(6n, n) + 1 is prime. Cf. A066699 = numbers n such that binomial(2n, n) + 1 is prime. Cf. A066726 = numbers n such that binomial(2n, n) - 1 is prime. Cf. A125220, A125221, A125240, A125241, A125242, A125243. Sequence in context: A053746 A327830 A144695 * A070416 A087168 A247560 Adjacent sequences:  A125241 A125242 A125243 * A125245 A125246 A125247 KEYWORD hard,more,nonn AUTHOR Alexander Adamchuk, Nov 25 2006 EXTENSIONS More terms from Ryan Propper, Mar 28 2007 a(18)-a(21) from Robert Price, May 13 2019 STATUS approved

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Last modified July 30 17:04 EDT 2021. Contains 346359 sequences. (Running on oeis4.)