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A220951 Primes p such that p+6 is also prime and there is a power of two in the interval (p,p+6). 2
5, 7, 11, 13, 31, 61, 251, 4093 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A search for sexy primes bracketing a power of two was conducted up to 2^1500. It is conjectured that this is a finite sequence.

On the basis of existing work about primes of the form 2^n+k and 2^n-k, plus a few additional tests, we have a(9) > 2^750740. - Giovanni Resta, Feb 21 2013

LINKS

Table of n, a(n) for n=1..8.

MATHEMATICA

pptQ[n_]:=AllTrue[{n, n+6}, PrimeQ]&&Count[Log[2, #]&/@Range[n, n+6], _?IntegerQ] > 0; Select[Range[4100], pptQ] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Nov 01 2015 *)

PROG

(MAGMA)

//Program finds primes separated by an even number (called gap) which have a power of two between them. Program starts with the smallest power of two above gap. Primes less than this starting point can be checked by inspection.

gap:=6;

start:=Ilog2(gap)+1;

for i:= start to 1000 do

   powerof2:=2^i;

   for k:=powerof2-gap+1 to powerof2-1 by 2 do

      if (IsPrime(k) and IsPrime(k+gap)) then

         k;

      end if;

   end for;

end for;

CROSSREFS

Cf. A023201, A220746, A221211.

Sequence in context: A135930 A163429 A339953 * A136055 A250127 A181494

Adjacent sequences:  A220948 A220949 A220950 * A220952 A220953 A220954

KEYWORD

nonn,more

AUTHOR

Brad Clardy, Feb 20 2013

STATUS

approved

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Last modified December 1 21:20 EST 2021. Contains 349435 sequences. (Running on oeis4.)