A263718 n such that (1+2*7^n)/3 is prime.

1, 3, 4, 15, 24, 58, 168, 234, 324, 375, 3327, 5788, 8344, 15039, 59116, 62620

Offset: 1

Author

James R. Buddenhagen, Oct 24 2015

Keywords

• nonn

Comments

The numbers corresponding to a(11)-a(16) are only (extra-strong BPSW) probable primes. - Charles R Greathouse IV, Nov 10 2015

Programs

Mathematica

Select[Range@ 2000, PrimeQ[(1 + 2 7^#)/3] &] (* Michael De Vlieger, Nov 06 2015 *)

PARI

is(n)=ispseudoprime((1+2*7^n)/3) \\ Charles R Greathouse IV, Nov 06 2015

Extensions

a(11)-a(14) from Charles R Greathouse IV, Nov 06 2015

a(15)-a(16) from Charles R Greathouse IV, Nov 09 2015