OFFSET
1,1
LINKS
Pierre CAMI, Table of n, a(n) for n = 1..1073
EXAMPLE
3*2^6 - 1 = 3*64 - 1 = 191 that is the 15th Sophie Germain prime, so a(6) = 3. - Bernard Schott, Sep 16 2019
PROG
(PARI) a(n) = my(k=1, p); while(!(isprime(p=3*k*2^n-1) && isprime(2*p+1)), k+=2); 3*k; \\ Michel Marcus, Sep 16 2019
(Magma) sol:=[]; for n in [1..50] do k:=3; while not IsPrime(k*2^n-1) or not IsPrime(2*(k*2^n-1)+1) do k:=k+6; end while; Append(~sol, k); end for; sol; // Marius A. Burtea, Sep 16 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Pierre CAMI, Apr 13 2010
EXTENSIONS
Name, data and b-file corrected by Michel Marcus, Sep 16 2019
STATUS
approved