A069179 - OEIS

%I #5 Oct 19 2017 03:14:00

%S 4,6,211050,253680,41887255410,73768891456260

%N Least number X such that for each k in (0 to n-1), 2^k*X-1 and 2^k*X+1 are primes. That is, there are N twin primes, each the "double" of the previous.

%C a(6)=73768891456260 might be called a(6.5), since 64*a(6)+1 is prime. But 64*a(6)-1 is 167*1021*44533*621769, alas.

%e a(3) = 211050 because 1*a(3)-1, 1*a(3)+1, 2*a(3)-1, 2*a(3)+1, 4*a(3)-1 and 4*a(3)+1 are all prime.

%Y Equals A068635 + 1.

%K nonn

%O 1,1

%A _Don Reble_, Apr 09 2002