login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A240765 Numbers n such that (43^n - 1)/42 is prime. 7
5, 13, 6277, 26777, 27299, 40031, 44773 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(8) > 10^5. - Robert Price, Apr 12 2014

LINKS

Table of n, a(n) for n=1..7.

H. Dubner, Generalized repunit primes, Math. Comp., 61 (1993), 927-930.

H. Lifchitz, Mersenne and Fermat primes field

MAPLE

A240765:=n->`if`(isprime((43^n - 1)/42), n, NULL); seq(A240765(n), n=1..100000); # Wesley Ivan Hurt, Apr 12 2014

MATHEMATICA

Select[Prime[Range[100000]], PrimeQ[(43^#-1)/42]&]

PROG

(PARI) is(n)=ispseudoprime((43^n-1)/42) \\ Charles R Greathouse IV, Feb 20 2017

CROSSREFS

Cf. A028491, A004061, A004062, A004063, A004023, A005808, A004064, A016054, A006032, A006033, A006034, A006035, A127995, A127996, A127997, A127998, A127999, A098438, A128002, A128003, A128004, A128005.

Sequence in context: A201260 A012173 A009143 * A127317 A049506 A069524

Adjacent sequences:  A240762 A240763 A240764 * A240766 A240767 A240768

KEYWORD

hard,more,nonn

AUTHOR

Robert Price, Apr 12 2014

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 07:59 EDT 2020. Contains 333079 sequences. (Running on oeis4.)