%N Numbers for which the least k > 1 which divides n + 2^k - 2 is different from the smallest prime factor of n.
%C Somewhat astonishingly, n = 89 is the only number below 173 for which the least prime factor is different from the least k > 1 which divides n + 2^k - 2. For larger n, this property becomes more frequent.
%C The first composite number in this sequence is a(105) = 3239.
%o (PARI) my(aa(n)=for(k=2,9e9,Mod(2,k)^k+n-2||return(k)));for(n=2,1e5,aa(n)!=factor(n)[1,1]&&print1(n","))
%A _M. F. Hasler_, Aug 11 2015