OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000 (from Bonath's link)
Karsten Bonath, First odd k for which k * 2^n - 1 and k * 2^(n + 1) - 1 are prime.
EXAMPLE
Example for n=7: a(7)=99 because 99*2^7-1 and 99*2^8-1 is the first occurrence for n=7 as a Sophie Germain prime pair.
MATHEMATICA
a[n_] := Module[{k = 1}, While[!And @@ PrimeQ[k * 2^{n, n+1} - 1], k += 2]; k]; Array[a, 30] (* Amiram Eldar, Jan 16 2020 *)
PROG
(Magma) a:=[]; for n in [1..55] do k:=1; while not (IsPrime(k*2^n-1) and IsPrime(k*2^(n+1)-1)) do k:=k+2; end while; Append(~a, k); end for; a; // Marius A. Burtea, Jan 16 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Karsten Bonath, Jul 23 2010
EXTENSIONS
More terms from Bonath's link added by Amiram Eldar, Jan 16 2020
STATUS
approved