A125244 Numbers k such that binomial(6k, k) - 1 is prime.

1, 7, 17, 22, 43, 343, 381, 461, 543, 923, 1045, 1182, 1486, 1839, 5643, 8260, 9009, 10947, 11793, 15915, 25151, 50923, 57095, 59977, 76513, 83383

Offset: 1

Author

Alexander Adamchuk, Nov 25 2006

Keywords

• hard
• more
• nonn

Comments

a(27) > 100000. - Robert Price, May 09 2025

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.

Programs

Mathematica

Do[f=Binomial[6n, n]-1; If[PrimeQ[f], Print[n]], {n, 1, 1000}]

Extensions

More terms from Ryan Propper, Mar 28 2007

a(18)-a(21) from Robert Price, May 13 2019

a(22)-a(23) from Georg Grasegger, May 08 2025

a(24)-a(26) from Robert Price, May 09 2025