OFFSET
1,1
COMMENTS
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.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
Chris K. Caldwell, Cunningham Chain.
Warut Roonguthai, Yves Gallot's Proth.exe and Cunningham Chains. [Wayback Machine link]
FORMULA
EXAMPLE
347 is a term because 173 is a prime but 695 is not.
MATHEMATICA
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 *)
PROG
(Python)
from itertools import count, islice
from sympy import isprime, prime
def A059452_gen(): # generator of terms
return filter(lambda p:isprime(p>>1) and not isprime(p<<1|1), (prime(i) for i in count(1)))
(PARI) is(p) = p > 2 && isprime(p) && isprime((p-1)/2) && !isprime(2*p+1); \\ Amiram Eldar, Jul 15 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Feb 02 2001
EXTENSIONS
Broken link updated by R. J. Mathar, Apr 12 2010
STATUS
approved