A128458 Numbers k such that 15^k - 2 is a prime.

1, 2, 3, 7, 12, 17, 19, 51, 65, 550, 1460, 1641, 7035, 18002, 20963, 21163, 42563, 94906, 148048

Offset

1,2

Comments

a(20) > 2*10^5. - Robert Price, Jun 23 2015

Links

Table of n, a(n) for n=1..19.

Mathematica

Do[ f = 15^n - 2; If[ PrimeQ[ f ], Print[ {n, f} ] ], {n, 1, 1000} ]
Do[If[PrimeQ[15^n - 2], Print[n]], {n, 10^4}] (* Ryan Propper, Jun 06 2007 *)

Crossrefs

Cf. A084714 (smallest prime of the form (2n-1)^k - 2).

Cf. A128472 (smallest prime of the form (2n-1)^k - 2 for k > (2n-1)).

Cf. A014224, A109080, A090669, A128455, A128457, A128459, A128460, A128461.

Sequence in context: A168249 A080140 A019568 * A066733 A049623 A302506

Adjacent sequences: A128455 A128456 A128457 * A128459 A128460 A128461

Keyword

nonn,hard,more

Author

Alexander Adamchuk, Mar 14 2007

Extensions

550 from Stefan Steinerberger, May 05 2007

3 more terms from Ryan Propper, Jun 06 2007

a(14)-a(19) from Robert Price, Jun 23 2015

Status

approved