A125245 Numbers k such that binomial(6k, k) + 1 is prime.

0, 1, 2, 4, 10, 15, 98, 111, 118, 236, 280, 512, 1284, 1303, 1818, 2525, 2692, 4620, 8405, 11539, 13190, 21525, 30338, 48069, 50687, 56208, 56620, 81091, 101488

Offset: 1

Author

Alexander Adamchuk, Nov 25 2006

Keywords

• hard
• more
• nonn

Comments

a(25) > 50000. - Robert Price, May 13 2019

Crossrefs

Cf. A125244 = 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(1)=0 and a(20)-a(24) from Robert Price, May 13 2019

a(25)-a(29) from Georg Grasegger, Jun 23 2025