login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A266163 Primes prime(k) such that (prime(k)*prime(k+1)+1)/2 is prime. 1
467, 2179, 2777, 4877, 6151, 6173, 6871, 7907, 7937, 8329, 9791, 11261, 11287, 12119, 12227, 12941, 13009, 14657, 14831, 15061, 15607, 16127, 16193, 16453, 16787, 16831, 17989, 18701, 18803, 18947, 19507, 20483, 20521, 20627, 22291, 22397, 22409, 22877, 23497 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

22397 and 22409 are first consecutive primes in this sequence. - Altug Alkan, Dec 22 2015

The next consecutive primes in this sequence are 134093 and 134129, 405541 and 405553, 432073 and 432097, 480803 and 480827, 586213 and 586237, ... - Harvey P. Dale, Dec 25 2015

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

MAPLE

lastp:= 3:

count:= 0:

while count < 100 do

  p:= nextprime(lastp);

  if isprime((lastp*p+1)/2) then

    count:= count+1;

    A[count]:= lastp;

  fi;

  lastp:= p;

od:

seq(A[i], i=1..100);

MATHEMATICA

Prime@ Select[Range@ 2620, PrimeQ[(Prime@ # Prime[# + 1] + 1)/2] &] (* Michael De Vlieger, Dec 22 2015 *)

Transpose[Select[Partition[Prime[Range[50000]], 2, 1], PrimeQ[ (Times@@#+1)/2]&]] [[1]] (* Harvey P. Dale, Dec 25 2015 *)

PROG

(PARI) lista(nn) = {forprime(p=3, nn, if(ispseudoprime((p*nextprime(p+1)+1)/2), print1(p, ", "))); } \\ Altug Alkan, Dec 22 2015

(MAGMA) [p: p in PrimesInInterval(3, 3*10^4) | IsPrime((p*NextPrime(p+1)+1) div 2)]; // Vincenzo Librandi, Dec 23 2015

CROSSREFS

Cf. A023524.

Sequence in context: A036339 A036340 A059395 * A221238 A114135 A043364

Adjacent sequences:  A266160 A266161 A266162 * A266164 A266165 A266166

KEYWORD

nonn

AUTHOR

Robert Israel, Dec 22 2015

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 21 06:36 EDT 2022. Contains 353889 sequences. (Running on oeis4.)