%I #11 Mar 30 2015 12:57:24

%S 1,1,3,45,45,15855,280665,4774980,4393585185,6522452145,166260770280,

%T 4321816939440,15939674132892510,22654052989616460555,

%U 22654052989616460555,202608454566431632290

%N Smallest i such that i*2^(2)-1, ..., i*2^(n+2)-1 are primes.

%C (2^2)*3-1=11, (2^3)*3-1=23 and (2^4)*3-1=47 are primes so 3 is the third entry.

%C For every x in A001122, the x-th term of this sequence and every succeeding term is divisible by x. For example 3 divides the 3rd and every succeeding term, 5 divides the 5th and every succeeding term.

%C The sequences of primes generated by these numbers are a type of Cunningham chain of the first kind (CC1). Since the longest known CC1 chain is of length 16, the next terms are currently unknown. - Douglas Stones (dssto1(AT)student.monash.edu.au), Mar 16 2005

%H Paul Jobling, <a href="http://www.utm.edu/research/primes/programs/NewPGen/">NewPGen</a>

%H G. Loeh, <a href="http://dx.doi.org/10.1090/S0025-5718-1989-0979939-8">Long chains of nearly doubled primes</a>, Mathematics of Computation, Vol. 53, No. 188, Oct 1989, pp. 751-759.

%Y Cf. A002515, A101790, A101794.

%K hard,nonn

%O 0,3

%A Douglas Stones (dssto1(AT)student.monash.edu.au), Dec 16 2004; revised Dec 31 2004

%E More terms from Douglas Stones (dssto1(AT)student.monash.edu.au), Mar 16 2005