%I A079543
%S A079543 74431,71528191,125780831,178708831,4150390625
%N A079543 Numbers n such that n has at least two distinct prime factors and if 
               a prime p divides n then (p-1)|(n-1) and (p+1)|(n+1).
%e A079543 a(1) = 74431 = 7^4 * 31 because 6 and 30 divide 74430 and 8 and 32 divide 
               74432.
%t A079543 Do[ f = Transpose[ FactorInteger[n]][[1]]; If[ Length[f] > 1 && Union[ 
               Mod[n - 1, f - 1]] == {0} && Union[ Mod[n + 1, f + 1]] == {0}, Print[n]], 
               {n, 6, 10^10}]
%Y A079543 Intersection of A056729 and A080062.
%Y A079543 Sequence in context: A023185 A105648 A122065 this_sequence A033450 A033448 
               A058415
%Y A079543 Adjacent sequences: A079540 A079541 A079542 this_sequence A079544 A079545 
               A079546
%K A079543 nonn
%O A079543 1,1
%A A079543 Don Reble (djr(AT)nk.ca), Jan 22 2003