login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A125956 Numbers n such that (2^n + 9^n)/11 is prime. 5
3, 7, 127, 283, 883, 1523, 4001 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All terms are primes. Note that first 3 terms (3, 7, 127} are primes of the form 2^q - 1, where q = {2, 3, 7) is prime too. Corresponding primes of the form (2^n + 9^n)/11 are {67, 434827, ...}.

a(8) > 10^5 - Robert Price, Dec 23 2012.

LINKS

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

MATHEMATICA

Do[p=Prime[n]; f=(2^p+9^p)/11; If[PrimeQ[f], Print[{p, f}]], {n, 1, 100}]

PROG

(PARI) is(n)=ispseudoprime((2^n+9^n)/11) \\ Charles R Greathouse IV, Feb 20 2017

CROSSREFS

Cf. A000978 = numbers n such that (2^n + 1)/3 is prime. Cf. A057469 = numbers n such that (2^n + 3^n)/5 is prime. Cf. A082387 = numbers n such that (2^n + 5^n)/7 is prime.

Sequence in context: A066771 A139159 A042329 * A260642 A128071 A079622

Adjacent sequences:  A125953 A125954 A125955 * A125957 A125958 A125959

KEYWORD

hard,more,nonn

AUTHOR

Alexander Adamchuk, Feb 06 2007

EXTENSIONS

2 more terms from Rick L. Shepherd, Feb 14 2007

a(7) from Robert Price, Dec 23 2012

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified September 24 22:31 EDT 2017. Contains 292441 sequences.