OFFSET
1,1
FORMULA
Equals (A060254 -1)/2.
MATHEMATICA
Select[ Range[ 225], PrimeQ[ # ] == PrimeQ[ # + 1] == False && PrimeQ[2# + 1] == True &] (* Robert G. Wilson v, Jul 11 2004 *)
PROG
(PARI) nextcomposite(k)=if(k<3, 4, if(isprime(k), k+1, k));
{m=230; n=4; while(n<m, k=nextcomposite(n+1); p=n+k; if(k==n+1&&isprime(p), print1(n, ", ")); n=k)} \\ Klaus Brockhaus, Jul 11 2004
(Magma)[n: n in [0..250]|not IsPrime(n) and not IsPrime(n+1) and IsPrime(2*n+1)] // Vincenzo Librandi, Dec 18 2010
CROSSREFS
KEYWORD
nonn
AUTHOR
Lekraj Beedassy, Jul 09 2004
EXTENSIONS
Corrected and extended by Klaus Brockhaus and Ray Chandler, Jul 10 2004
STATUS
approved