A057018 Numbers k such that (10*7^k -1)/3 is prime.

0, 1, 2, 14, 29, 38, 40, 59, 62, 64, 76, 80, 101, 491, 1024, 1814, 1826, 13733

Offset

1,3

Comments

No further terms through k = 5000. - Harvey P. Dale, Jan 09 2016

a(19) > 20941. - Jinyuan Wang, Dec 27 2019

Links

Table of n, a(n) for n=1..18.

Mathematica

Do[ If[ PrimeQ[ (10*7^n -1)/3 ], Print[ n ] ], {n, 0, 2500} ]
Select[Range[0, 1900], PrimeQ[(10*7^#-1)/3]&] (* Harvey P. Dale, Jan 09 2016 *)

Prog

(PARI) is(n)=ispseudoprime((10*7^n-1)/3) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Cf. A057437.

Sequence in context: A189331 A157023 A101554 * A038341 A075718 A259710

Adjacent sequences: A057015 A057016 A057017 * A057019 A057020 A057021

Keyword

nonn,more

Author

Robert G. Wilson v, Sep 09 2000

Extensions

a(18) from Jinyuan Wang, Dec 27 2019

Status

approved