A128458 - OEIS

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

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OFFSET

1,2

COMMENTS

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

LINKS

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)).

KEYWORD

nonn,hard,more

AUTHOR

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