1,1

a(1) = 74431 = 7^4 * 31 because 6 and 30 divide 74430 and 8 and 32 divide 74432.

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}]

Intersection of A056729 and A080062.

Sequence in context: A023185 A105648 A122065 this_sequence A033450 A033448 A058415

Adjacent sequences: A079540 A079541 A079542 this_sequence A079544 A079545 A079546

nonn

Don Reble (djr(AT)nk.ca), Jan 22 2003