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A059608 Numbers n such that 2^n - 5 is prime. 21
3, 4, 6, 8, 10, 12, 18, 20, 26, 32, 36, 56, 66, 118, 130, 150, 166, 206, 226, 550, 706, 810, 1136, 1228, 1818, 2368, 2400, 3128, 4532, 5112, 8492, 16028, 16386, 17392, 18582, 21986, 24292, 27618, 30918, 32762, 48212, 120440, 183632, 316140, 364982, 414032 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Except 3, all terms are even since for odd n, 2^n - 5 is divisible by 3.

LINKS

Table of n, a(n) for n=1..46.

Keith Conrad, Square patterns and infinitude of primes, University of Connecticut, 2019.

Henri Lifchitz & Renaud Lifchitz (Editors), Search for 2^n-5, PRP Top Records

MATHEMATICA

Select[Range[2, 20000], PrimeQ[2^# - 5] &] (* Vladimir Joseph Stephan Orlovsky, Feb 26 2011 *)

PROG

(PARI) is(n)=isprime(2^n-5) \\ Charles R Greathouse IV, Feb 17 2017

CROSSREFS

Exponents for primes of 2^n-d form: A000043 (d=1), A050414 (d=3), A059608 (d=5), A059609 (d=7), A059610 (d=9), A096817 (d=11), A096818 (d=13), A059612 (d=15), A059611 (d=17), A096819 (d=19), A096820 (d=21).

Sequence in context: A092137 A206580 A291899 * A088071 A247422 A256698

Adjacent sequences:  A059605 A059606 A059607 * A059609 A059610 A059611

KEYWORD

nonn

AUTHOR

Andrey V. Kulsha, Jan 30 2001

EXTENSIONS

a(32)-a(34) from Labos Elemer, Jul 09 2004

a(35)-a(40) from Max Alekseyev, a(41) from Paul Underwood, a(42)-a(46) from Henri Lifchitz, added by Max Alekseyev, Feb 09 2012

STATUS

approved

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Last modified April 15 13:37 EDT 2021. Contains 342977 sequences. (Running on oeis4.)