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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
OFFSET
1,2
COMMENTS
a(22) > 50000. - Robert Price, May 13 2019
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
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