A128455 Numbers k such that 9^k - 2 is a prime.

1, 2, 3, 11, 45, 51, 260, 324, 390, 393, 1112, 3092, 4445, 10373, 15861, 18528, 97715, 112961

Offset: 1

Author

Alexander Adamchuk, Mar 14 2007

Keywords

• nonn
• hard
• more

Comments

a(19) > 2*10^5. - Robert Price, Aug 18 2014

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, A128457, A128458, A128459, A128460, A128461.

Programs

Mathematica

Do[ f = 9^n - 2; If[ PrimeQ[ f ], Print[ {n, f} ] ], {n,1,1000} ]

Extensions

1112 from Stefan Steinerberger, May 05 2007

More terms from Ryan Propper, Jan 12 2008

a(15)-a(18) from Robert Price, Aug 18 2014