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



(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A059452 Safe primes (A005385) which are not Sophie Germain primes. 23


%S 7,47,59,107,167,227,263,347,383,467,479,503,563,587,839,863,887,983,

%T 1187,1283,1307,1319,1367,1487,1523,1619,1823,1907,2027,2099,2207,

%U 2447,2579,2879,2999,3119,3167,3203,3467,3947,4007,4079,4127,4139,4259,4283

%N Safe primes (A005385) which are not Sophie Germain primes.

%C A156659(a(n))*(1-A156660(a(n))) = 1. - _Reinhard Zumkeller_, Feb 18 2009

%H C. K. Caldwell, <a href="http://primes.utm.edu/glossary/page.php?sort=cunninghamchain">Cunningham Chain</a>

%H W. Roonguthai, <a href="http://ksc9.th.com/warut/cunningham.html">Yves Gallot's Proth.exe and Cunningham Chains</a>

%e 347 is here because 173 is a prime but 695 is not. Except for 7, these primes are congruent to 11 modulo 12. Terminal primes in complete Cunningham chains of first kind, i.e., the chains cannot be continued from these primes.

%t lst={};Do[p=Prime[n];If[PrimeQ[(p-1)/2],If[ !PrimeQ[2*p+1],AppendTo[lst,p]]],{n,6!}];lst (* _Vladimir Joseph Stephan Orlovsky_, Jun 24 2009 *)

%Y Cf. A005384, A005385, A053176, A059452-A059456, A007700, A005602, A023272, A023302, A023330.

%K nonn

%O 1,1

%A _Labos Elemer_, Feb 02 2001

%E Broken link updated by _R. J. Mathar_, Apr 12 2010

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 September 20 19:48 EDT 2020. Contains 337265 sequences. (Running on oeis4.)