On the unboundedness of common divisors of distinct terms of the   sequence $a_n=2^{2^n}+d$ for $d>1$
  It is well-known that for any distinct positive integers $k$ and $n$, the numbers $2^{2^k}+1$ and $2^{2^n}+1$ are relatively prime. In this paper we consider the situation when 1 is replaced by some positive integer $d>1$ 
Tigran Hakobyan
math.NT