OFFSET
1,1
COMMENTS
For all numbers N not listed in A260868, the least k > 1 that divides N + 2^k - 2 is equal to the least prime factor of N.
It appears that the range of this sequence is A267999. For example, 155 occurs first somewhat late for N = 2729. - Corrected by Thomas Ordowski, Oct 27 2018
PROG
(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(aa(n)", "))
CROSSREFS
KEYWORD
nonn
AUTHOR
M. F. Hasler, Aug 11 2015
STATUS
approved