A125240 Numbers k such that binomial(4k, k) - 1 is prime.

1, 16, 36, 67, 95, 369, 383, 745, 1599, 2006, 2104, 2879, 3061, 9048, 9902, 12369, 15058, 18858, 21287, 22759, 24674, 33899, 43730, 55078, 86085

Offset: 1

Author

Alexander Adamchuk, Nov 25 2006

Keywords

• hard
• more
• nonn

Comments

a(26) > 10^5 - Robert Price, Sep 15 2024

Crossrefs

Cf. A125241 = numbers n such that binomial(4n, 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, A125242, A125243, A125244, A125245.

Programs

Mathematica

Do[f=Binomial[4n, n]-1; If[PrimeQ[f], Print[n]], {n, 1, 1000}]

Extensions

More terms from Ryan Propper, Mar 28 2007

a(16)-a(23) from Robert Price, Apr 30 2019

a(24)-a(25) from Robert Price, Sep 15 2024